OCT  5    1905 


YV\  . 


\ 
LIBRARY 

OF    THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


ROCK   EXCAVATION 


METHODS  AND  COST 


ALBERT  POWERS  GILLETTE 

M.  Am.  Soc.  C.  E.,  M.  Am.  InU.  M.  E. 

E.  M.  School  of  Mines,  Columbia  University 

Late  Assistant  New  York  State  Engineer 


NEW  YORK 

.    C.    CLARK 
13-21  Park  Row 
1904 


•MIMING* 


Copyright,  1904, 

By 
M.    C.    CLARK. 


PREFACE. 

The  value  of  the  mineral  products  of  America  annually 
exceeds  $1,000,000,000.  For  explosives  alone  the  sum  of 
$20,000,000  is  expended  each  year,  and  it  is  well  within 
limits  to  say  that  fully  twice  as  great  a  sum  is  paid  out  to 
drillers  and  blasters.  When  we  consider  the  labor,  the  power 
and  the  powder  required  to  mine  and  to  quarry  products  in 
the  aggregate  so  enormously  valuable,  we  can  not  fail  to  be 
impressed  with  the  scantiness  of  literature  on  the  economics  . 
of  rock  excavation.  A  dozen  years  ago,  when  called  upon  to 
estimate  the  cost  of  some  open  cut  rock  excavation,  I  was 
astonished  to  find  no  text  book  that  in  the  least  served  to 
guide  me.  I  subsequently  learned  also  that  most  of  the  mat- 
ter to  be  found  in  the  few  books  on  blasting  was  either 
theoretic  or  too  meagre  to  be  of  material  value.  What  was 
true  then  has  unfortunately  remained  true. 

In  the  preparation  of  this  volume,  it  was  my  original  in- 
tention to  give  only  condensed  cost  data  on  rock  excava- 
tion— including  in  that  term,  quarrying,  open  cut  work, 
trenching,  tunneling,  and  underground  excavation;  but,  as 
the  writing  progressed,  it  become  more  and  more  apparent 
that  methods  of  doing  work  and  "tricks  of  the  trade"  should 
occupy  an  important  part  of  the  book  to  make  it  at  all  satis- 
factory. I  saw  that  my  object  should  be  not  merely  to  fur- 
nish data  whereby  an  inexperienced  man  might  predict  the 
cost  of  rock  work  with  at  least  tolerable  accuracy,  but  that  it 
should  be  my  aim  also  to  indicate  to  the  experienced  man- 
ager how  and  where  savings  in  the  cost  of  production  may 
be  effected. 

Taking  my  own  notes  and  records  of  cost  as  a  basis,  I 
have  added  so  extensively  to  them  by  correspondence  that 
the  reader  will  find  not  a  little  on  costs  that  has  never  ap- 
peared in  print  before.  In  addition,  I  have  abstracted  scores 
of  pages  of  facts  and  figures  from  the  volumes  of  scientific 

137438 


iv  PREFACE. 

and  engineering  periodicals,  due  acknowledgement  of  which 
appears  throughout  the  text. 

While  the  scope  of  the  book  is  wider  than  at  first  sight  ap- 
pears desirable,  since  it  includes  quarrying,  open  cut  excava- 
tion, trenching,  subaqueous  excavation,  tunneling  and  un- 
derground excavation,  still  it  should  be  remembered  that  the 
main  elements  of  cost  are  of  much  the  same  quality,  and 
that  the  differences  are  principally  those  of  quantity.  Thus, 
it  may  require  eight  feet  of  drill  hole  per  cubic  yard  of  tun- 
nel excavation  as  compared  with  half  a  foot  for  open  cut 
work.  The  cost  of  drilling  per  cubic  yard  is  obviously  much 
greater  in  the  tunnel  than  in  the  open  cut,  but  the  methods 
of  drilling  and  the  cost  per  foot  of  drill  hole  may  be  prac- 
tically identical.  There  is,  indeed,  much  in  common  in  all 
classes  of  rock  excavation  in  spite  of  many  detailed  differ- 
ences. 

For  these  reasons,  and  because  my  training  and  exper- 
ience have  been  both  in  mine  and  in  quarry  work,  I  have 
chosen  for  this  book  the  broad  scope  indicated  by  its  title. 
I  am  well  aware  of  defects  in  the  execution  of  my  plan,  but 
trust,  however,  that  suggestions  as  to  sources  of  information 
now  unknown  to  me,  and  original  data  will  be  sent  to  me  by 
readers  who  are  interested  in  the  progress  of  the  art  of 
economic  excavation.  There  is  probably  not  a  man  of  any 
considerable  experience  who  could  not  add  his  quota  of 
valuable  information,  if  he  would ;  and,  on  the  other  hand, 
there  is  not  one  of  us  who  "knows  it  all1' — except  the  fellow 
who  really  knows  very  little.  Men  engaged  in  mining  can 
learn  from  those  whose  excavation  work  is  in  the  open  air, 
and  the  reverse  holds  equally  true.  The  mining  engineer 
profits  to-day  by  inventions  developed  under  the  direction  of 
civil  engineers,  and  thousands  of  civil  engineers  in  turn  are 
indebted  to  mining  engineers.  It  is  well  for  us  not  to  forget 
that  the  first  air  drill,  so  useful  in  mining,  was  the  develop- 
ment of  work  in  a  railway  tunnel,  and  that  the  first  railway 
was  the  development  of  work  in  a  mine. 

New  York,  Sept.,  1904.  HALBERT  P.  GILLETTE. 


CONTENTS. 


PAGE 

CHAPTER    L— Rocks    and 

Their  Properties   i 

Rock-forming  Minerals    . .  I 

Hardness  2 

Rock  Species   3 

Joints    4 

Veins  and  Beds 5 

Shale    6 

Sandstone    6 

Limestone 6 

Granite    7 

Porphyry 7 

Trap    8 

Weight  and  Voids 8 

Tables  of  Weights  of  Rock  9 

Measurement  of  Rock....  n 

CHAPTER  II.  —  Methods 
and  Cost  of  Hand  Drill- 
ing    13 

Kinds  of  Hand  Drills....  13 

Theory  of  Drilling 13 

Hammer  Drilling 17 

One-Hand   vs.    Two-Hand 

Drilling    18 

Churn  Drilling  18 

Cost  of  Hammer  Drilling.  19 

Cost  of  Churn  Drilling...  22 

Hand-Drill  Bits   23 

Sharpening  Hand  Drills..  26 

Sharpening  Machine  Drills  29 

CHAPTER  III.  —  Machine 

Drills  and  Their  Use...  31 

Machine  Drill  Mechanism.  31 

Sizes  of  Air  Drills 32 

Handling  Drill  on  Tripod.  34 

Use  of  Column  or  Bar. ...  40 

Use  of  Water  in  Drilling.  43 
Other    Types    of    Machine 

Drills 45 


PAGE 

CHAPTER  IV.— Steam  and 

Compressed  Air  Plants.     47 
Heat    Energy    and    Horse 

Power 47 

The  Work  of  Compression  49 
Tests  of  Air  Consumed  by 

Drills   Si 

Tests  of  Air  Consumption 

at  the  Rose  Deep  Mine.     55 
Tables    of    Air    Consump- 
tion in  Catalogs 56 

Steam  Consumption  in 
Terms  of  Air  Consump- 
tion    58 

Efficiency    of    Steam    Pipe 

Line   60 

Flow     of     Air     Through 

Pipes    63 

Fuel  and  Boiler  Efficiency.  65 
Merits  of  Compressed  Air  68 
Efficiency  of  the  Jerome 

Reservoir  Plant   69 

Gasoline  Air  Compressors.     70 
CHAPTER    V.—The    Cost 
of  Machine  Drilling. ...     72 

Cost  Factors   72 

Percentage  of  Lost  Time.     73 
Results    of    Drilling    Con- 
tests         78 

Rule  for   Estimating  Feet 

Drilled  per  Shift 79 

Rates  of  Drilling  in  Dif- 
ferent Rocks  82 

Average    Footage    Drilled 

per    Shift    84 

Cost  of  Sharpening  Bits.     85 

Cost  of  Drill  Repairs 86 

Plant  Rental   86 

Cost  of  Installing  a  Com- 
pressor Plant  87 


VI 


CONTENTS. 


PAGE 

Cast  of  a  Large  Com- 
pressor Plant 88 

Cost  of  Operating  Drills.  .     89 

Cost  of  Drilling  Blast 
Holes  with  Well  Drill- 
ers   90 

Cost  of  Drilling  with  Elec- 
tric Drills  93 

CHAPTER     VI.— Cost     of 

Diamond  Drilling   95 

Price  of  Diamonds 96 

Water  Required  96 

Price  of  Diamond  Drills..  97 
Cost    of   Drilling    in    Vir- 
ginia      97 

Cost  of  Drilling  in  Lehigh 

Valley    101 

Cost  on  Croton  Aqueduct.  102 
Cost  of  Hand  Drilling  in 

Arizona    103 

References  on  Costs 105 

CHAPTER    VII.  —  Explo- 
sives      106 

The  Action  of  Gases 106 

Black  Powder  108 

Properties  of  Good  Pow- 
der    109 

Dynamite  and  Nitroglycer- 
ine    no 

Varieties  of  Dynamite....  in 

The  Absorbent  114 

Weight  of  Dynamite 115 

Thawing  Dynamite 116 

How  to  Thaw  Dynamite.   119 
Testing       Dynamite       for 

Safety    121 

Blasting  Gelatin  121 

Judson   Powder    122 

Joveite    122 

CHAPTER     VIII.— Charg- 
ing and  Firing 124 


PAGE 

Kind  of  Explosive  to  Use.  124 

Charging  Black  Powder.  .  126 

Charging  Dynamite 127 

Firing  by  Electricity 131 

Misfires    134 

Methods  of  Firing 136 

Safety  Fuse 136 

Caps  I36 

Electric   Detonators    139 

CHAPTER  IX.  -  Methods 

of  Blasting  141 

The  Theory  of  Blasting. .   141 

Placing  Drill   Holes 146 

Springing  Holes 147 

Blasting  with  Powder  and 
Dynamite  Together  ....  149 

Large  Chamber  Blasts 150 

Blasting  Hardpan   156 

Blasting  Piles  and  Stumps  160 

Ice  Blasting 162 

Boulder  Blasting   162 

CHAPTER  X.  —  Cost  of 
Loading  and  Transport- 
ing Rock  • 164 

Cost  of  Loading  by  Hand.   164 

Cost  of  Handling  Crushed 
Stone  165 

Cost  of  Handling  with 
Derricks  166 

Cost  of  Loading  with 
Steam  Shovels  168 

Cost  of  Steam  Shovel 
Work  in  Iron  Ore 173 

Cost  of  Hauling  in  Wheel- 
barrows    176 

Cost  of  Hauling  in  Carts 
and  Wagons 177 

Hauling  qn  Stone  Boats..   181 

Cost  of  Hauling  in  Dump 
Cars  .  .  182 


CONTENTS. 


Vll 


PAGE 

CHAPTER  XL— Quarrying 

Stone   184 

General  Considerations  .  . .    184 

Joints  186 

Plug  and  Feathers 187 

Cost  of   Plug   Drilling  by 

Hand   189 

Cost    of    Pneumatic    Plug 

Drilling   189 

The  Quarry  Bar 191 

Broaching    192 

The  Gadder 192 

The  Channeler   193 

Cost  of  a  Quarry  Derrick.  196 
Knox  System  of  Blasting.  197 
Cost  of  Quarrying  by 

Knox  System 198 

Cost  of  Quarrying  Dimen- 
sion Sandstone   202 

Quarrying  by  Water  Cush- 
ion Blasts  203 

Granite  Quarrying 204 

Quarrying  Massive  Granite  207 
Cost  of  Quarrying  Granite  208 
Cost   of   Quarrying    Sand- 
stone Rubble  211 

Cost   of   Quarrying  Lime- 
stone     212 

CHAPTER  XlL—Open  Cut 

Excavation  214 

General  Considerations  .  . .  214 
Excavation  in  Benches...  214 

Spacing  Holes 216 

Cost    of    Quarrying    Trap 

for   Macadam    218 

Cost     of     Quarrying     and 

Crushing  Limestone.  . . .  220 
Cost  of  Pit  Mining,  Brews- 

ter,  N.  Y 221 

Cost  of  Excavating  Gneiss  222 
Cost  of  Excavating  Sand- 
stone and  Shale 223 


PAGE 

Cost  of  Railroad  Excava- 
tion in  Tennessee 225 

Cost      of      Blasting      and 

Sledging  Boulders 232 

Summary  236 

Table    of    Explosives    and 
Drilling   per    Cu.    Yd...  237 

CHAPTER  XIII.  —  Meth- 
ods and  Costs  on  the 
Chicago  Drainage  Canal  238 

General  Conditions   238 

Excavating    Very     Tough 

Clay    239 

Excavating  Hardpan 239 

Incline  and  Tipple 243 

Cost  by  Lidgerwood  Cable- 
ways  244 

Cost   by    Hullett-McMyler 

Cantilever  Crane  250 

Cost    by    Hullett-McMyler 

Derrick   252 

Cost  by  Geraldine  Double- 
Boom  Derrick 254 

Cost  by  Brown  Cantilever 

Crane 255 

Cost  by  Car  Hoists 258 

Summary  of  Costs 261 

Cost   of   Channeling 262 

Cost  of  Drilling 264 

Steam    Shovel   Output 265 


CHAPTER   XIV.— Cost   of 

Trenches  and  Subways.  267 
General  Considerations  .  .  267 
Method  of  Charging  Holes  268 

Blasting  Mats  269 

Cost  of  Drilling  and  Blast- 
ing    270 

Cost    of    N.    Y.     Subway 
Work  273 


Vlll 


CONTENTS. 


PAGE 

CHAPTER    XV.— Subaque- 
ous Excavation 277 

Cost    of    Excavation,    De- 
troit River   277 

Cost    of    Harbor    Excava- 
tion, Oswego,  N.  Y....  284 
Cost  of  Excavating  Black 

Tom   Reef,   N.   Y 287 

Cost       of       Undermining 

Flood  Rock,  N.  Y 289 

The   Derby   Tubular   Drill 

Bit  290 

Drilling      and       Dredging 

Way's  Reef,  N.  Y 291 

Cost  of  Excavation,  Eagle 

Harbor,   Mich 292 

Cost   of   Excavation,    Pier 

14,    N.    Y 293 

Drilling      and      Dredging 

Boulders   295 

Drilling  in  San  Francisco 

Harbor  296 

CHAPTER    XVI. -Cost   of 

Railway   Tunnels   297 

The  American  System. . . .  297 
A  Device  for  Laying  Dust 

with  Water 299 

The  Gallitzin  Tunnel 299 

Cost    of    Wabash    R.    R. 

Tunnels 302 

Cost  of  the  Stampede  Tun- 
nel    307 

Cost  of  Mount  Wood  and 

Top  Hill  Tunnels 313 

Cost    of    a    Hand-Driven 

Tunnel  on  the  B.  &  O. .  315 
Cost  of  New  Croton  Tun- 
nel Work  318 

Cascade  Tunnel  Data 323 

Kellogg  Tunnell   Data 325 

Pryor  Gap  Tunnel  Data. .  326 
Busk  Tunnel  Data 327 


PAGE 

Sutro  Tunnel  Data 328 

Musconetcong  Tunnel  Data  329 
'A  Tunnel  through  the  Pali- 
sades,   N.   J 330 

Methods  Used  in  the  Te- 

quixqueac  Tunnel 331 

The  Simplon  Tunnel 332 

Cost    of    a    Tunnel    near 

Peekskill,  N.  Y 336 

Cost  of  Lining  Tunnels..  338 

CHAPTER  XVII.— Cost  of 
Drifting,  Shaft  Sinking 
and  Stoping  341 

Definitions  341 

Cost  of  Tunneling,  Mel- 
ones  Mine  343 

Cost  of  Tunneling,  Hogs- 
back  Mine  345 

Cost  of  Sinking  and  Stop- 
ing  at  the  Utica  Angels  346 

Cost  of  Sinking  and  Drift- 
ing at  the  Lincoln  Gold 
Mine  347 

Cost  of  the  Newhouse 
Tunnel 35o 

Cost  of  Sinking  and  Drift- 
ing at  the  Homestake 
Mine  353 

Cost  of  Drifting  and  Stop- 
ing  at  Cripple  Creek.  . .  .  356 

Cost  of  Drifting  and  Stop- 
ing  at  Rossland,  B.  C.  .  359 

Cost  of  Development  and 
Stoping,  Centre  Star 
Mine,  B.  C 361 

Cost  of  Shaft  Sinking  at 
the  Pioneer  Mine 363 

Cost  of  Two  Three-Com- 
partment Shafts  365 

Lost  of  Mining,  Douglas 
Island,  Alaska  366 


ROCKS  AND  THEIR  PROPERTIES. 

Rock-forming  Minerals. — All  rocks  are  aggregates  of  one 
or  more  minerals  or  the  disintegrated  products  of  minerals. 
A  mineral  is  an  inorganic  body  having  a  definite  chemical 
composition,  as  quartz,  common  salt,  mica,  and  the  like. 
There  are  about  1,000  distinct  species  of  minerals,  but  for- 
tunately the  common  rock-forming  minerals  number  less 
than  30;  and  of  these  30  perhaps  15  should  be  recognized  at 
sight  by  everyone  who  aims  to  become  an  expert  in  rock 
excavation. 

A  small  cabinet  of  the  common  species  of  minerals  may 
be  purchased  for  a  few  dollars  from  any  of  the  dealers  whose 
advertisements  may  be  found  in  the  mining  and  civil  engi- 
neering journals.  Such  a  cabinet  when  studied  with  the  aid 
of  a  small  book  on  mineralogy  will  enable  one  to  undertake 
the  work  of  rock  excavation  intelligently.  It  is  often  said 
that  "a  little  knowledge  is  a  dangerous  thing";  but  a  little 
knowledge  of  fundamental  principles,  whether  of  geology 
or  of  any  other  of  the  physical  sciences,  is  exactly  the  oppo- 
site of  dangerous.  A  little  knowledge  of  a  few  scientific 
facts,  it  is  true,  often  leads  to  incorrect  rules  or  generaliza- 
tion ;  but  a  knowledge  of  correct  rules  and  fundamental  prin- 
ciples, based  upon  the  observation  and  study  of  many  facts 
by  experts,  is  the  kind  of  little  knowledge  that  no  man  can 
afford  to  be  without.  Thus,  for  example,  geologists  classify 
rocks  according  to  their  origin  into  two  great  classes,  (i) 
sedimentary  or  stratified,  and  (2)  crystalline,  or  igneous. 
A  contractor,  who  had  lost  many  thousand  dollars  on  some 
rock  excavation  in  the  northern  part  of  New  York,  once  told 
me  that  he  attributed  his  loss  to  a  lack  of  knowledge  of 


2  ROCK  EXCAVATION— METHODS  AND  COST. 

geology.  His  previous  experience  had  been  confined  to  the 
shales  and  sandstones  of  Pennsylvania.  When  he  came  to 
estimate  the  cost  of  excavating  a  granitic  rock  he  made  due 
allowance  for  its  greater  hardness  and  toughness  as  affecting 
the  speed  of  drilling ;  but  he  failed  to  consider  the  fact  that 
the  absence  of  lines  of  stratification  in  the  granite  would 
necessitate  placing  drill  holes  much  closer  together  than  in 
shale  or  sandstone.  The  result  was  that  not  only  the  cost 
of  drilling  but  the  cost  of  explosives  per  cubic  yard  of  granite 
excavation  was  practically  double  what  he  had  counted  upon. 

Every  mining  man  can  cite  many  striking  instances  to 
show  how  ignorance  of  the  elementary  facts  of  geology  and 
petrology  have  lead  to  serious  underestimates  of  the  cost 
of  tunneling,  shaft  sinking  and  stoping.  It  is  true  that  where 
an  engineer,  contractor  or  miner  works  all  his  life  in  one 
locality  he  becomes  so  expert  in  his  knowledge  of  the  meth- 
ods and  cost  of  rock  excavation  that  he  sees  little  prac- 
tical value  to  himself  in  a  knowledge  of  minerals,  rocks  or 
geologic  principles.  But  when,  possibly  late  in  life,  he  goes 
to  a  new  field  of  action,  he  is  likely  to  lose  his  reputation,  if 
not  his  money,  through  lack  of  a  "little  knowledge"  of  the 
fundamental  principles  of  rock  formation.  The  science 
which  he  has  regarded  as  being  too  theoretical  for  him 
might  have  saved  him  had  he  possessed  even  a  little  of  it. 

I  therefore  repeat  that  the  man  who  aims  to  become  an 
expert  in  all  kinds  of  rock  excavation,  should  first  learn  to 
know  the  common  species  of  minerals  at  sight,  or  by  means 
of  the  simple  tests  described  in  books  on  mineralogy.  It  is 
beyond  the  province  of  this  book,  however,  to  describe 
rocks  and  rock  forming  minerals.  There  are  several  excel- 
lent books  on  that  subject,  with  one  or  more  of  which  the 
rock  excavator  should  be  familiar. 

Hardness. — The  resistance  to  scratching  or  cutting  is 
termed  hardness.  Diamond  is  the  hardest  mineral  known, 
as  it  will  scratch  all  others.  Talc  is  one  of  the  softest  miner- 
als. Mineralogists  use  a  scale  of  hardness  as  follows : 


ROCKS  AND  THEIR  PROPERTIES.         3 

1.  Talc.  6.  Feldspar. 

2.  Gypsum.  7.  Quartz. 

3.  Calcite.  8.  Topaz. 

4.  Fluorite.  9.  Corundum. 

5.  Apatite.  10.  Diamond. 

The  sharpest  point  of  a  steel  knife  will  not  scratch  quartz, 
but  under  considerable  pressure  will  scratch  feldspar.  A  very 
slight  pressure  on  the  knife  will  scratch  talc  or  gypsum ;  in- 
deed the  finger  nail  will  serve  to  scratch  them.  The  test  of 
hardness  often  serves  to  distinguish  one  mineral  from  an- 
other ;  for  instance,  iron  pyrites  and  copper  pyrites  are  simi- 
lar in  color,  but  while  copper  pyrites  can  be  scratched  with 
a  knife,  iron  pyrites  cannot.  To  distinguish  sandstone  from 
limestone  it  is  often  necessary  merely  to  draw  a  sharp  corner 
of  the  stone  across  a  pane  of  glass.  If  a  scratch  is  left  in 
the  glass  the  stone  can  not  be  pure  limestone,  since  calcite, 
which  has  a  hardness  of  3,  is  the  mineral  forming  limestone. 
Impure  limestone  may  be  a  mixture  of  fine  grains  of  quartz 
and  calcite;  but  after  a  little  experience  in  testing  stones 
and  minerals  the  eye  will  aid  to  such  a  degree  in  determining 
the  species  that  the  test  of  hardness  becomes  a  very  reliable 
one  in  many  cases. 

Hardness  of  course  affects  the  speed  of  drilling  in  rock, 
although  to  a  less  degree  than  toughness.  A  tough  rock  is 
one  that  will  stand  a  hard  blow  without  splintering.  Win- 
dow glass  is  quite  hard,  almost  as  hard  as  tempered  steel, 
but  it  is  not  very  tough.  Sandstone  is  hard,  so  far  as  its 
individual  grains  are  concerned,  but  is  often  drilled  with 
ease,  since  it  usually  lacks  in  toughness.  Trap  rock  is  both 
hard  and  tough,  and  makes  drilling  difficult,  besides  dulling 
the  drill  rapidly. 

Rock  Species. — Rocks  may  be  classified  as:  (i)  Sedi- 
mentary; (2)  igneous,  and  (3)  metamorphic.  Sedimentary 
rocks  have  been  deposited  originally  from  suspension  or 
solution  in  water;  thus  sand  hardened  into  rock  becomes 
sandstone ;  clay  becomes  shale  or  slate ;  gravel  becomes  con- 


4  ROCK  EXCAVATION— METHODS  AND  COST. 

glomerate  or  pudding  stone;  wood  fiber  becomes  peat  or 
coal;  shells  of  minute  forms  of  sea  life  form  limestone,  or 
possibly  lime  in  solution  crystallizes  out  as  does  rock  salt. 
The  chief  characteristic  of  sedimentary  rocks  is  that  they  lie 
in  beds  or  layers,  one  upon  the  other,  often  not  cemented  to- 
gether in  the  slightest  degree;  and  even  where  they  appear 
to  be  solid  and  massive  they  can  usually  be  split  into  slabs 
by  wedging. 

The  igneous  rocks  have  at  one  time  been  in  a  molten 
condition,  and  include  the  traps,  porphyries,  most  granites, 
and  all  volcanic  lavas,  etc.  Igneous  rocks  are  often  exceed- 
ingly tough,  hard  to  drill,  and  are  apt  to  break  out  in  very  ir- 
regular masses,  sometimes  of  huge  size  and  in  other  cases 
of  too  small  a  size  to  make  cut  stone  masonry. 

The  metamorphic  rocks,  may  be  said  to  be  a  "cross  be- 
tween" the  sedimentary  and  the  igneous  rocks,  for  they  have 
been  formed  by  chemical  and  physical  changes  in  sedi- 
mentary rock  under  the  influence  of  heat,  water  and  pres- 
sure. For  example,  a  dike  of  molten  rock  rising  through  a 
fissure  in  shale  heats  the  surrounding  shale  to  such  a  degree 
that,  in  the  presence  of  confined  water,  the  shale  dissolves 
or  melts,  and,  when  it  solidifies  by  subsequent  cooling,  a 
gneiss  is  produced.  Some  granites  are  known  to  have  been 
made  in  this  way  by  what  is  called  metamorphic  action. 
Marble  is  metamorphosed  limestone,  and  quartzite  is  meta- 
morphosed sandstone. 

Joints. — All  rocks  are  more  or  less  split  up  along  vertical 
or  nearly  vertical  planes  termed,  joints,  which  greatly  assist  in 
the  quarrying.  Joints  are  the  results  of  stress,  due  to  shrink- 
age of  the  earth's  crust  upon  cooling.  This  shrinkage  has 
produced  great  compression  in  some  places  and  tension  in 
others,  resulting  in  cracking  of  the  rock  masses  at  more  or 
less  regular  intervals. 

In  limestone  and  in  close  grained  shales  the  joints  are  often 
regular  but  so  close  as  to  be  invisible  until  revealed  by  frac- 
ture or  by  weathering.  In  coarse  grained  sedimentary  rocks, 


ROCKS  AND  THEIR  PROPERTIES.         5 

the  joints  are  apt  to  be  more  open  and  irregular,  running 
into  one  another  or  branching. 

In  sedimentary,  rocks  there  are  generally  two  sets  of 
joints  running  approximately  at  right  angles,  known  as  the 
dip-joints  and  the  strike-joints.  The  "dip"  of  the  rock  is 
the  angle  that  its  bedding  planes  make  with  a  horizontal 
plane.  The  "strike"  is  the  line  of  intersection  between  an  in- 
clined plane  and  a  horizontal  plane ;  thus,  if  a  sheet  of  car J- 
board  be  held  at  an  incline  in  a  basin  of  water,  the  line  of  the 
water  surface  along  the  face  of  the  cardboard  is  the  "strike/' 
Since  a  quarry  is  usually  worked  to  the  dip  of  the  rock,  the 
strike  joints,  or  "backs,"  form  clean  cut  faces  in  front  of 
the  workmen  as  they  advance;  while  the  dip  joints,  or  "cut- 
ters" form  the  side  faces  of  the  benches  in  the  quarry.  Thus 
it  happens  that  in  some  sedimentary  stone  quarries,  nature 
has  provided  blocks  of  stone,  practically  loose  on  all  six 
faces ;  but,  as  a  rule,  the  joints  are  so  irregularly  spaced  as  to 
require  much  plug  and  feathering  work. 

Igneous  rocks,  while  not  possessing  bedding  planes,  also 
have  nearly  vertical  joints,  cutting  at  about  right  angles  in 
most  cases ;  but  these  joints  are  seldom  so  regular  in  spacing 
as  in  sedimentary  rocks.  In  certain  trap  rocks  the  joints 
cause  the  rock  to  break  out  in  vertical  columns,  often  of 
great  regularity;  and  in  some  cases  the  joints  are  so  close 
together  that  upon  firing  the  blast  the  rock  comes  down  in 
chunks  not  much  larger  than  a  man's  head,  even  where  very 
little  explosive  is  used ;  but,  on  the  other  hand,  certain  traps 
break  up  in  very  large  chunks  on  blasting. 

Veins  and  Beds. — Iron  ores  and  coal  occur  for  the  most 
part  in  beds  that  originally  were  nearly  horizontal,  since  they 
are  of  sedimentary  origin.  They  are,  or  at  one  time  have 
been,  overlaid  by  sedimentary  rocks. 

Veins  carrying  the  ores  of  the  valuable  metals  are  in  some 
cases  fissures  or  cavities  that  have  been  filled  by  hot  waters 
carrying  minerals  in  solution.  These  fissure  veins  exist  in 
both  sedimentary  and  in  igneous  rocks,  but  as  a  rule  near 


6  ROCK  EXCAVATION— METHODS  AND  COST. 

dikes  or  sheets  of  igneous  rocks  that  were  at  one  time  in  a 
molten  state. 

Limestone. — As  its  name  implies,  limestone  is  the  rock 
from  which  lime  is  made.  It  is  seldom  pure  (calcite),  but 
usually  contains  more  or  less  clay  and  often  silica.  By  dis- 
solving some  powdered  limestone  in  nitric  acid  the  amount  of 
impurity  may  be  roughly  ascertained,  for  neither  clay  nor 
quartz  is  dissolved  by  the  acid.  In  some  cases  it  will  be 
found  that  there  is  less  limestone  than  clay  in  the  so-called 
limestone.  Due  to  the  presence  of  impurities,  few  rocks 
vary  more  in  compactness  and  appearance  than  does  lime- 
stone. When  pure,  it  is  hard  and  crystalline;  but  friable, 
chalky  deposits  of  limestone  are  not  uncommon.  The  com- 
mon color  is  a  gray,  or  a  blue  gray,  passing  into  white. 
Marble  is  a  pure  metamorphosed  limestone.  Dolomite  is  a 
magnesian  limestone  in  which  part  of  the  lime  has  been  re- 
placed by  magnesia. 

Sandstone. — As  its  name  implies,  sandstone  is  sand  ce- 
mented together.  The  cementing  material  is  commonly 
silica  or  iron  oxide  (iron  rust).  When  cemented  by  silica 
the  rock  is  apt  to  be  very  tough  and  far  more  durable  than 
when  cemented  by  iron  rust;  and  is  consequently  more  diffi- 
cult to  drill.  Sandstone  generally  contains  enough  iron 
oxide  to  give  it  a  red  or  brown  color.  White  sandstone,  as 
well  as  dark  blue,  is  quite  common.  Sandstone  often  con- 
tains enough  clay  to  make  it  difficult  to  classify  it;  in  such 
cases  it  is  usually  very  fine  grained  and  may  be  mistaken  for 
slate,  especially  when  it  splits  into  thin  slabs. 

Shale. — Shale  is  really  a  baked  clay  or  mud,  generally 
yellow,  brown  or  black  in  color,  and  easily  split  into  leaves. 
Under  great  pressure  shale  has  often  been  converted  into 
slate  in  which  the  pressure  has  forced  the  long  particles  into 
a  position  perpendicular  to  the  line  of  pressure,  and  im- 
parted lines  of  cleavage  entirely  independent  of  the  original 
bedding  planes  of  the  shale.  Shales  often  contain  silica  and 
lime  to  a  degree  that  makes  their  classification  puzzling.  Dry 


ROCKS  AND  THEIR  PROPERTIES.         7 

clay  upon  absorbing  water  swells,  so  that  clays  which  have 
been  only  partly  baked  into  shale  absorb  water  upon  ex- 
posure and  go  to  pieces ;  moreover,  the  swelling  often  causes 
great  difficulty  in  tunnelling  or  shaft  sinking,  since  the  force 
developed  by  absorbing  water  may  crush  or  displace  the  tim- 
bers used  in  lining. 

On  the  other  hand  well  hardened  shales  do  not  swell  upon 
exposure  and,  if  not  exposed  to  great  changes  in  tempera- 
ture, have  a  long  life.  It  often  becomes  a  very  important 
economic  question  to  decide  whether  a  tunnel  through  shale 
should  be  lined  with  concrete  or  masonry,  and  many  civil 
engineers  have  made  serious  blunders  through  lack  of  scien- 
tific knowledge  of  the  properties  of  the  different  shales.  If 
an  engineer  has  had  experience  only  with  half-baked  shales, 
he  is  apt  to  line  with  masonry  every  permanent  tunnel  that 
he  builds  in  shale,  regardless  of  the  kind  of  shale;  while, 
on  the  other  hand,  an  engineer  whose  experience  has  been 
with  well  baked  shales  may  err  by  failing  to  provide  lining 
for  tunnels  in  half-baked  shales.  I  could  mention  several 
instances  of  economic  errors  of  this  kind,  but  I  have  perhaps 
emphasized  sufficiently  the  advantage  possessed  by  the  en- 
gineer who  has  a  good  working  knowledge  of  rocks  and  of 
geology. 

Granite. — Granite  is  composed  of  quartz,  feldspar  and 
mica;  the  quartz  acting  as  the  cement  binding  the  whole 
together  in  a  crystalline  mass.  When  the  percentage  of 
feldspar  is  large  the  granite  is  said  to  be  porphyritic.  The 
mean  specific  gravity  is  about  2.65. 

Porphyry. — Porphyry  is  an  overworked  name  applied  by 
miners  to  almost  any  igneous  rock  whose  real  name  they  do 
not  know.  Quartz-porphyry,  or  felsite,  is  composed  of 
quartz  and  feldspar;  when  the  quartz  is  visible  as  well- 
marked  grains  or  crystals,  the  rock  is  generally  called  quartz- 
porphyry  ;  but  when  the  quartz  and  feldspar  are  so  intimately 
mixed  as  not  to  be  readily  distinguished,  the  term  felsite 
is  more  often  used. 


8  ROCK  EXCAVATION— METHODS  AND  COST. 

Trap. — Trap  is  another  overworked  name,  that  is  com- 
monly applied  to  fine  grained  rocks  of  igneous  origin. 
Among  the  trap  rocks  are :  Diabase,  diorite,  basalt,  etc.  The 
trap  rocks  usually  have  irregular  joints,  and,  while  on  ac- 
count of  their  toughness  they  may  be  excellent  material  for 
macadam,  they  are  seldom  fit  for  building  purposes,  except 
when  crushed  and  used  in  concrete.  The  Hudson  River  trap, 
diabase,  has  a  specific  gravity  of  about  2.95. 

Weight  and  Voids.  — Civil  engineers  commonly  measure 
rock  excavation  by  the  cubic  yard  in  place  before  loosen- 
ing, whereas  mining  engineers  generally  use  the  ton  of 
2,000  pounds,  as  the  unit  of  rock  and  ore  measurement.  In 
view  of  this  fact  it  would  be  well  were  the  specific  gravity 
of  the  rock  given  by  every  engineer  who  publishes  data  on 
any  particular  kind  of  rock  excavation  or  mining.  Then, 
too,  it  often  happens  that  broken  rock  is  purchased  by  the 
ton  even  for  civil  engineering  work,  or  by  the  cord  of  loosely 
piled  rubble  for  architectural  work,  thus  emphasizing  the  im- 
portance of  stating  not  only  the  specific  gravity  but  the 
percentage  of  voids. 

The  specific  gravity  of  any  material  is  the  quotient  found 
by  dividing  its  weight  by  the  weight  of  an  equal  bulk  of 
water.  Water,  therefore,  has  a  specific  gravity  of  I  ;  a 
cubic  foot  of  any  substance  like  granite,  having  a  specific 
gravity  of  2.65,  weighs  2.65  times  as  much  as  a  cubic  foot  of 
water.  A  cubic  foot  of  water  weighs  62.355  Ibs.,  or  prac- 
tically 62.4  Ibs. ;  hence  a  cubic  foot  of  solid  granite  weighs, 
2.65  X  62.4  =  165.3  lbs- 

When  any  rock  is  crushed  or  broken  into  fragments  of 
tolerably  uniform  size  it  increases  in  bulk,  and  is  found  to 
have  35  per  cent,  to  55  per  cent,  voids  or  inter-spaces,  de- 
pending upon  the  uniformity  pf  the  fragments  and  their  an- 
gularity. Rounded  fragments,  like  pebbles,  pack  more  closely 
together  than  sharp-edcred  or  angular  fragments.  A  tumbler 
full  of  bird  shot  has  about  36  per  cent,  voids,  and  it  is  pos- 
sible to  hand-pack  marbles  of  uniform  size,  so  that  the  voMs 


ROCKS  AND  THEIR  PROPERTIES.         9 

are  only  26  per  cent.  Obviously,  if  small  fragments  of  stone 
are  mixed  with  large  fragments  the  voids  are  reduced.  Pit 
sand  ordinarily  has  35  to  40  per  cent,  voids.  Hard  broken 
stone  from  a  rock  crusher  has  about  35  per  cent,  voids  if  all 
sizes  are  mixed  and  slightly  shaken  down  in  a  box ;  whereas, 
if  it  is  screened  into  several  sizes,  each  size  has  about  45  to 
48  per  cent,  voids. 

A  soft  and  friable  rock-like  shale  breaks  into  fragments 
having  a  great  range  in  size,  from  large  chunks  down  to 
dust;  and,  as  a  consequence,  such  soft  broken  rocks  have  a 
much  lower  percentage  of  voids  than  the  tougher  rocks. 

The  following  table  shows  the  swelling  of  rock  upon 
breaking: 


Voids 30%    35%    40%    45%    5o%    55% 

No.   of  cu.   yds.    (loose   incas-^ 

ure)  made  by  each  cu.  yd.  [-1.43      1.54     1.67      1.82     2.00     2.22 

of  solid  rock. .  .  J 


Hard  rock  when  blasted  out  in  large  chunks  and  thrown 
into  cars  or  skips  may  ordinarily  be  assumed  to  have  from 
40  to  45  per  cent,  voids,  hence  I  cu.  yd.  of  hard  solid  rock  or- 
dinarily makes  1.67  to  1.82  cu.  yds.  of  broken,  or  crushed 
rock. 

Tables  of  Weights  of  Rock. — Tables  I.  and  II.  will  be  found 
useful  for  computing  the  weight  of  solid  or  broken  rock 
from  the  specific  gravity.  Thus,  suppose  it  is  desired  to  as- 
certain the  weight  of  a  solid  cubic  yard  of  granite,  also  the 
weight  of  a  cubic  yard  of  crushed  granite  having  about  40 
per  cent,  voids.  In  Table  I.  it  is  seen  that  granite  has  a  spe- 
cific gravity  of  2.55  to  2.86;  assuming  2.7  as  an  average  and 
turning  to  Table  II.,  we  find  that  a  rock  having  a  specific 
gravity  of  2.7  weighs  4,546  Ibs.  per  cu.  yd.  solid,  or  2,727  Ibs. 
per  cu.  yd.  when  broken  up,  so  that  40  per  cent,  of  the  masb 
is  voids. 


io          ROCK  EXCAVATION— METHODS  AND  COST. 

TABLE  I. 

SPECIFIC    GRAVITY    OF    COMMON    MINERALS    AND   ROCKS. 

Apatite  2.92—3.25  Limestone    2.35—2.87 

Basalt  3.01  Magnetite,  Fe3C)4 4.9  — 5.2 

Calcite,  CaCO3 2.5  —2.73  Marble   2.08—2.85 

Cassiterite,   SnO2 6.4—7.1  Mica   2.75—3.1 

Cerrusite,   PbCO, 6.46—6.48  Mica    Schist 2.5  —2.9 

Chalcopyrite,  CuFeSz.  4.1  — 4.3  Olivine    3.33 — 3.5 

Coal,  anthracite 1.3  — 1.84  Porphyry  2.5  — 2.6 

Coal,  bituminous 1.2—1.5  Pyrite,  FeS2 4.83—5.2 

Diabase  2.6  —3.03  Quartz,  SiO2 2.5  —2.8 

Diorite   2.92  Quartzite  2.6 — 2.7 

Dolomite,CaMg(CO3)2  2.8  — 2.9  Sandstone    2.0  — 2.78 

Feldspar   2.44 — 2.78  Medina    ...  2.4 

Felsite  2.65  Ohio   2.2 

Galena,   PbS 7.25—7.77  Slaty 1.82 

Garnet 3.15—4.31  Shale   2.4  —2.8 

Gneiss    2.62 — 2.92  Slate  2.5  — 2.8 

Granite 2.55 — 2.86  Sphalerite,   ZnS 3.9 — 4.2 

Gypsum    2.3  —3.28  Stibnite,   Sb2S3 4.5  —4.6 

Halite   (salt),  NaCl. .  2.1  —2.56  Syenite    2.27—2.65 

Hematite,    Fe2O3 4.5  —5.3  Talc  2.56—2.8 

Hornblende   3.05 — 3.47  Trap   2.6  — 3.0 

Limonite,  Fe3O4(OH)e  3.6  —4.0 

TABLE  II. 

tC  i_  sg  u 

IT;  sal     '+•»  Q«  •       .H  o,*d  Weight  in  Lbs.  per  cu.  yd.  when 

'§*     .'Ijs"       .'IjS*  _Voids^are 

1.0       62.355 

2.0  1247 

2.1  130.9 

2.2  137.2 

2.3  1434 

2.4  1497 
2-5  155-9 

2.6  162.1 

2.7  168.4 

2.8  174.6 

2.9  180.9 
3.0  187.1 
3-1  193-3 
3-2  199-5 
3-3  205.8 

3.4          212.0 
3-5          218.3 

On  the  other  hand,  if  the  weight  per  cubic  yard  of  the 
loose  broken  stone  is  known  (as  is  often  the  case),  and  if 


£      ° 

30% 

35% 

40% 

45% 

50% 

1,684 

1,178 

1,094 

1,010 

926 

842 

3,367 

2,357 

2,187 

2,020 

1,852 

1,684 

3,536 

2,475 

2,298 

2,121 

1,945 

1,768 

3,704 

2,593 

2,408 

2,222 

2,037 

1,852 

3,872 

2,711 

2,517 

2,323 

2,130 

1,936 

4,041 

2,828 

2,626 

2,424 

2,222 

2,020 

4,209 

2,946 

2,736 

2,525 

2,315 

2,105 

4,377 

3,064 

2,845 

2,626 

2,408 

2,189 

4,546 

3,182 

2,955 

2,727 

2,500 

2,273 

3,300 

3,064 

2,828 

2,593 

2,357 

4882 

3,4i8 

3,174 

2,929 

2,685 

2,441 

3,536 

3,283 

3,030 

2,778 

2,526 

5',2i9 

3,653 

3,392 

3,131 

2,871 

2,609 

5.388 

3,77i 

3,502 

3,232 

2,963 

2,694 

5,556 

3,889 

3,6n 

3,333 

3,056 

2,778 

5,724 

4,007 

3,72i 

3,434 

3,148 

2,862 

5,893 

4,125 

3,830 

3,535 

3,241 

2,947 

ROCKS  AND   THEIR  PROPERTIES.  11 

the  specific  gravity  has  been  determined  by  a  test,  then  Table 
II.  can  be  used  to  find  the  per  cent,  of  voids  in  the  broken 
stone.  Thus,  if  a  given  sandstone  has  been  found  to  have 
a  specific  gravity  of  2.4,  and  .upon  shipping  in  cars  it  has 
been  found  to  weigh  2,200  Ibs.  per  cu.  yd.,  measured  loose  in 
the  car  box,  then  from  Table  II.,  it  is  seen  that  about  45  per 
cent,  of  the  mass  of  broken  stone  is  voids. 

Measurement  of  Rock. — Sedimentary  rock  quarried  in 
slabs  that  are  corded  up  carefully  by  hand  may  have  30  per 
cent.,  or  less,  voids,  which  makes  it  evident  that  a  contractor 
in  buying  rock  by  the  cord  should  be  careful  to  specify  that 
it  be  packed  closely  and  not  dumped  in  piles  helter  skelter 
before  measurement.  In  buying  rock  by  the  "cord"  there  is 
another  precaution  to  be  taken,  and  that  is  to  specify  how 
many  cubic  feet  constitute  a  cord.  A  cord  of  wood  is  4  X 
4X8=  128  cu.  ft.,  but  a  ucord"  of  stone  is  commonly  i  X 
4  X  8  =  32  cu.  ft.  Likewise  the  word  perch,  when  used, 
should  be  clearly  defined.  A  perch  of  masonry  is  commonly 
taken  as  being  25  cu.  ft.  (or  nearly  I  cu.  yd.),  but  the  original 
perch  was  a  wall  12  ins.  high,  18  ins.  wide  and  a  rod  (16% 
ft.)  long,  making  24^4  cu.  ft.  In  certain  localities  the  "perch" 
is  taken  as  being  only  22  cu.  ft.  These  facts  the  contractor 
should  know,  for  he  must  often  deal  with  quarrymen  who 
will  not  sell  rock  by  the  cubic  yard. 

Rock  is  often  purchased  by  the  ton  of  2,000  Ibs. ;  but  to 
avoid  lawsuits  it  is  wise  to  define  the  word  "ton"  in  any  writ- 
ten or  verbal  contract,  for  a  ton  means  2,240  Ibs.  in  some 
localities. 

If  crushed  stone  for  macadam  or  ballast  is  purchased  by 
the  cubic  yard  measured  loose,  the  precaution  of  stating 
where  the  measurement  is  to  be  made  should  always  be  taken. 
I  have  made  measurements  of  wagon  loads  of  broken  stone 
after  loading  from  chutes  at  the  bins,  and  again  after  travel- 
ing for  half  a  mile  or  more.  A  surprising  shaking  down,  or 
settlement,  always  takes  place,  ordinarily  making  a  reduc- 
tion in  volume  of  10  per  cent. 


12          ROCK  EXCAVATION— METHODS  AND  COST. 

Rock  excavation  is  commonly  measured  in  place  before 
loosening  and  paid  for  by  the  cubic  yard  of  actual  excava- 
tion ;  but,  in  sewer  work  and  in  tunnel  work,  if  the  contractor 
excavates  beyond  certain  "neat  lines"  shown  in  the  blue- 
prints, no  payment  is  made,  unless  the  specifications  ex- 
plicitly provide  for  payment  for  excavation  beyond  these 
"neat  lines."  In  trench  work,  for  example,  a  contractor  often 
has  to  excavate  from  6  to  18  ins.  below  the  grade  shown  in 
the  blue-print,  because  it  costs  less  to  do  so  than  to  work  too 
close  to  the  grade  and  afterward  break  off  projecting  knobs 
with  a  bull-point  or  otherwise.  The  same  is  true  of  shallow 
excavation,  or  skimming  work,  in  road  construction  and  the 
like. 

In  examining  specifications  care  should  also  be  taken  to 
note  whether  mention  is  made  of  rock  slips  or  falls ;  for  it 
often  happens  that  after  blasting  to  the  neat  lines  a  huge  slide 
of  rock  occurs,  possibly  filling  the  entire  excavation.  Who 
is  to  stand  the  cost  of  removing  this  slide?  If  it  is  specified 
that  the  contractor  shall,  then  he  should  study  the  dip  of 
the  rock  and  its  character  with  this  question  of  sliding  in 
mind. 

It  is  occasionally  specified  that  rock  for  rip-rap  shall  be 
paid  for  by  the  cubic  yard  after  deposition ;  although  it  is  a 
most  unsatisfactory  and  uncertain  way,  for  much  of  the  rock 
may  be  lost  in  the  mud  or  rolled  away  by  the  current.  If 
the  rock  is  delivered  in  scows  it  is  a  simple  matter  to  estimate 
its  weight  by  water  displacement. 


CHAPTER  II. 
METHODS  AND  COST  OF  HAND  DRILLING. 

Kinds  of  Hand  Drills. — Drilling  holes  in  rock  by  hand  may 
be  effected  in  three  ways  :  ( I )  By  a  rotary  drill  or  auger ; 
(2)  by  a  churn-drill;  (3)  by  a  hammer-drill,  or  "jumper" 
drill,  struck  with  a  hammer.  A  rock  auger  operated  by  hand 
is  used  only  in  very  soft  rock  or  coal. 

A  churn-drill,  as  its  name  implies,  is  raised  and  allowed  to 
drop,  or  is  hurled  against  the  rock.  For  shallow  holes  of 
small  diameter  it  is  necessary  to  give  a  churn-drill  additional 
weight,  which  is  done  by  welding  a  ball  of  wrought  iron  to 
the  center  of  the  drill  shank,  making  a  ball-drill.  A  ball-drill 
is  usually  provided  with  a  cutting  bit  at  each  end  and  is  oper- 
ated by  one  man.  For  deep  drilling,  that  is,  for  holes  more 
than  about  2^/2  or  3  ft.  deep,  an  ordinary  churn-drill  is  used, 
operated  by  one  man  for  shallow  work,  two  men  for  deeper 
work  and  three  or  even  four  men  for  very  deep  holes  where 
the  weight  of  metal  becomes  considerable. 

The  Theory  of  Drilling. — A  hammer-drill,  often  called  a 
"jumper,"  although  it  is  not  jumped,  may  be  driven  by  one 
man,  who  holds  the  drill  with  one  hand  and  strikes  it  with  a 
hammer  in  the  other  hand.  In  this  way  holes  up  to  3  ft.  in 
depth  can  ordinarily  be  drilled  cheaper  than  when  one  man 
holds  the  drill  while  two  men  strike.  But  in  discussing  the 
relative  economy  of  one-hand  drilling  as  compared  with  two- 
hand  drilling,  authorities  appear  to  have  ignored  the  factor 
of  depth  of  hole.  As  the  hole  grows  deeper  the  advantage 
of  a  heavy  hammer  becomes  more  and  more  apparent ;  but  a 
heavy  hammer  requires  a  man's  two  arms  to  swing  it.  A 
large  percentage  of  the  energy  of  the  blow  is  always  con- 

13 


14          ROCK  EXCAVATION— METHODS  AND  COST. 

sumed  in  compressing  the  head  of  the  drill,  the  shank  of  the 
drill  and  the  hammer  itself,  leaving  at  best  only  a  small  per- 
centage to  overcome  the  cohesion  of  the  rock  with  the  drill 
bit.  In  pile  driving  in  soft  mud  about  65  per  cent,  of  the 
energy  of  the  hammer  is  lost  in  heating  the  pile-head,  etc., 
leaving  only  35  per  cent,  to  overcome  the  friction  of  the  mud 
on  the  pile ;  and  in  an  analogous  way  much  of  the  energy  of 
a  hammer  in  the  hands  of  a  driller  is  lost.  The  longer  the 
pile  and  the  lighter  the  pile  hammer,  the  greater  the  loss  of 
energy  and  the  less  effective  the  blow ;  so  in  drilling  there 
comes  with  increased  length  of  drill  a  decreased  percentage 
of  energy  that  reaches  the  bit.  In  fact,  if  the  drill  be  made 
long  enough,  the  blow  of  a  one-hand  hammer  has  absolutely 
no  effect  in  cutting  the  rock,  although  a  two-hand  hammer 
still  has  effect. 

The  churn-drill  in  the  hands  of  a  skilled  driller  is  the  most 
effective  type  of  hand  drill  for  vertical  holes ;  and  a  little 
theory  is  not  without  its  practical  value  in  seeking  the  reason 
for  the  effectiveness  of  the  churn-drill.  As  before  stated, 
much  of  the  energy  of  the  blow  of  a  hammer  is  lost  in  the 
form  of  heat  at  the  head  of  the  drill.  This  loss  does  not  oc- 
cur with  the  churn-drill.  Moreover,  the  element  of  time  in- 
volved in  wedging  off  a  chip  of  rock  also  appears  to  be  an  im- 
portant factor.  When  the  cutting  edge,  or  wedge,  of  a  churn- 
drill  first  reaches  the  bottom  of  the  hole,  after  its  descent,  the 
work  of  wedging  off  a  rock  chip  begins.  A  wave  of  com- 
pression travels  up  several  feet  of  steel  before  the  last  ounce 
of  steel  in  the  drill  bar  has  done  its  work.  Obviously  it  must 
take  about  12  times  longer  for  a  churn-drill  6  ft.  long  to  do 
its  wedging  work  than  for  a  hammer  6  ins.  long  to  do  its 
work.  This  comparatively  gradual  and  steadily  increasing 
wedging  action  of  the  churn-drill  theoretically  should  be 
more  effective  than  the  more  sudden  action  of  a  hammer- 
drill  ;  and,  as  a  matter  of  fact,  it  is. 

It  takes  some  skill  to  start  a  hole  with  a  ball-drill  and  to 
keep  it  plumb ;  but  the  time  spent  in  acquiring  this  skill  is  re- 


METHODS  AND  COST  OF  HAND  DRILLING.          15 

paid  many  times  over  if  quarry  operations  with  hand-drills 
are  to  be  moderately  extensive. 

The  effect  of  the  size  of  the  hole  upon  the  speed  of  drilling 
appears  never  to  have  been  carefully  determined.  One  au- 
thority says  that  to  double  the  diameter  of  the  hole  decreases 
the  speed  of  drilling  by  one-half.  Another  authority  thinks 
that  doubling  the  diameter  divides  the  speed  by  four.  Ac- 
cording to  the  first  authority,  if  a  man  could  drill  12  ft.  of 
i  in.  hole  in  a  shift,  he  could  drill  only  6  ft.  of  2-in.  hole  in  a 
shift.  According  to  the  second  authority,  only  3  ft.  of  2-in. 
hole  could  be  drilled  per  shift.  As  bearing  upon  this  point 
the  reader  is  referred  to  some  experiments  with  different 
sizes  of  bits  used  in  machine-drilling  tests,  an  abstract  of 
which  appears  on  page  54. 

In  drilling  by  hand  it  is  evident  that  the  blow  of  a  hammer 
is  most  effective  when  directed  vertically  downward,  less  ef- 
fective when  directed  horizontally  and  least  effective  when  di- 
rected upward.  The  only  careful  experiments  to  determine 
the  relative  speeds  of  drilling  at  different  angles  appear  to  be 
those  of  Prof.  Hofer.  The  time  required  to  drill  I  inch  of 
hole  in  graywacke  (a  slate,  or  grit,  or  conglomerate?)  with 
a  hammer-drill,  with  holes  at  different  angles,  was  as 
follows : 

85°  down  (nearly  vertical)  152  sees. 

60°       "        188     " 

52°       " 241     " 

27°       "        282     " 

2°         "  257      " 

o°  (horizontal)   323     " 

24°  up 345 

From  which  it  appears  that,  at  these  rates,  16  ft.  of  vertical 
hole  or  7^  ft.  of  horizontal  hole  would  be  drilled  in  8  hrs. 
This  shows  one  of  the  several  reasons  why  rock  excavation 
in  a  tunnel  by  hand  is  more  expensive  than  open  cut  excava- 
tion ;  and  it  indicates  the  importance  of  stating  the  angle  of 


16          ROCK  EXCAVATION— METHODS  AND  COST. 

the  drill  hole  when  giving  data  on  hand  drilling.  Some  data 
given  by  Jarolimek  on  drilling  dolomitic  limestone  roughly 
confirm  the  above : 

60°  down 10,3  sees. 

10°  up 287     " 

45°  up 345     " 

As  bearing  upon  this  point  of  the  angle  at  which  holes  are 
drilled  some  old  data  may  be  quoted  from  Schoen's  "Der 
Tunnelblau"  (1874).  Schoen  gives  the  comparative  num- 
ber of  cubic  yards  of  material  excaved  in  an  open  cut  and 
in  a  railway  tunnel,  by  hand  work,  8-hr,  shift,  and  using 
black  powder : 

Cu.  yds  per  man,  8  hrs. 

Tunnel.  Open  cut. 

Soft  ground 8.5  16.2 

Ground  loosened  with  pick 5.3  7.2 

*     gad    3.2  6.5 

Quarried  rock  i.i  2.6 

Quarried  and  blasted  rock 0.64  2.0 

Blasted  rock 0.34  1.3 

In  considering  the  effectiveness  of  vertical  hole  drilling 
it  should  be  remembered  that  a  hole  which  can  be  kept 
partly  full  of  water  can  ordinarily  be  drilled  faster  than  a 
dry  hole,  and  holes  that  "look  up"  are  necessarily  dry,  unless, 
as  is  rarely  done,  a  jet  of  water  is  kept  playing  into  the  hole. 
The  water  in  a  down  hole  takes  up  and  holds  in  suspension 
the  fine  particles  of  rock,  leaving  a  clean  face  of  rock  at  the 
bottom  of  the  hole  for  the  bit  to  work  upon.  One  authority 
(Aitken)  says  that  in  quarrying  trap  rock  the  use  of  water 
in  drilling  reduces  the  time  of  drilling  a  hole  by  30  per  cent. 
In  certain  so'ft  shales,  however,  up  holes  are  drilled  faster 
than  down  holes,  for  the  dry  powdered  shale  runs  out  of  the 
up  hole ;  but  in  a  down  hole  the  shale  powder  makes  a  stiff 
mud  with  the  water  and  cushions  the  blow  of  the  bit. 


METHODS  AND  COST  OF  HAND  DRILLING.          17 

Hammer  Drilling. — The  common  weight  of  hammer  for 
one-hand  drilling  is  4>4  Ibs. ;  for  two-hand  or  three-hand 
drilling,  10  Ibs.  The  striking  face  must  be  flat  or  slightly 
rounding,  and  smaller  than  the  stock  of  the  hammer.  The 
hole  is  started  on  a  solid  and  squared  surface,  with  a  short 
drill,  for  the  longer  the  drill  the  less  effective  the  blow.  Light 
blows  are  struck  at  first.  The  bit  is  turned  one-eighth  of  a 
revolution  after  each  blow  to  insure  keeping  the  hole  truly 
circular.  But  in  spite  of  this  precaution  most  hand-drilled 
holes  are  three-cornered,  or  "rifled."  This  rifling  is  not 
very  objectionable  in  ordinary  excavation  work,  but  in  quar- 
rying square  blocks  for  masonry  it  is  decidedly  objection- 
able because  the  rock  tends  to  split  in  the  directions  of  the 
three  angles  of  the  drill  hole  upon  blasting.  How  to  pre- 
vent this  rifling  will  be  shown  in  a  subsequent  paragraph. 

A  leather  or  rubber  washer  is  slipped  over  the  drill  and 
kept  close  to  the  hole  to  prevent  splashing  of  the  sludge  into 
the  eyes  of  the  drillers.  Water  is  poured  into  the  hole,  an 
operation  which  is  called  "tending  chuck."  The  water  holds 
the  powdered  rock  in  suspension,  forming  a  sludge  which 
must  be  removed  from  time  to  time.  For  cleaning  out  this 
sludge  a  scraper  or  "spoon"  is  used  in  shallow  holes.  A 
spoon  is  a  ^  to  ^-in.  rod  provided  with  a  disc  at  each  end, 
the  discs  being  of  different  diameters  to  correspond  with 
the  size  of  the  hole  at  different  depths.  A  spiral  hook,  or 
drag-twist,  is  also  used  for  wiping  the  hole  with  hay  before 
charging  with  black  powder.  A  wooden  rod,  split  or  broomed 
at  the  end  is  often  used  for  cleaning  out  a  hole.  The  broomed 
end  of  the  rod  is  dipped  into  the  sludge,  and  when  removed 
from  the  hole  is  struck  upon  the  rock  to  remove  the  sludge 
adhering  to  the  broomed  end. 

For  two-hand  or  three-hand  hammer  drilling  a  bit  of  1^4 
to  1 5/2  ins.  is  commonly  used  for  the  starter,  and  the  ex- 
treme depth  of  hole  is  ordinarily  not  over  6  or  8  ft. ;  for, 
as  previously  shown,  the  effectiveness  of  the  hammer  blow 
falls  off  rapidly  with  increased  depth.  One  man  holding 


i8          ROCK  EXCAVATION— METHODS  AND  COST. 

the  drill  and  two  men  striking  (three-hand  drilling)  form 
the  most  effective  gang  for  railway  tunnel  work,  also  for 
quarry  work  where  men  used  to  churn  drilling  are  not 
available. 

One-Hand  vs.  Two-Hand  Drilling. — In  the  metal  mines  of 
the  West  skilled  miners  ordinarily  prefer  one-hand  drilling 
when  working  by  contract.  The  miner  holds  the  drill  with 
one  hand  and  wields  the  hammer  with  the  other.  In  very 
hard  rock  two-hand  drilling  is  said  by  Drinker  to  be  slightly 
(15  per  cent.)  cheaper  than  one-hand  drilling;  but  in  soft 
rock  he  says  one-hand  drilling  is  20  to  30  per  cent,  cheaper 
than  two-hand  drilling.  Where  one  man  strikes,  while  the 
other  man  holds  the  drill,  the  heavier  hammer  used  makes  it 
possible  to  drill  a  larger  and  deeper  hole  with  economy. 
Where  there  is  room  for  one  man  to  hold  while  two  men 
strike,  the  economy  is  greater  still.  In  American  railway 
tunnel  work  two  or  three-hand  drilling  is  much  more  com- 
monly seen  than  one-hand  drilling.  Reliable  data  showing 
the  relative  economy  of  one,  two  and  three-hand  drilling', 
using  different  diameters  and  lengths  of  bit,  are  not  to  be 
found  in  print,  although  much  to  be  desired. 

Churn  Drilling. — For  drilling  vertical  holes,  churn  drilling 
is  cheaper  than  hammer  drilling.  The  only  exception  to  this 
statement  is  the  drilling  of  plug  and  feather  holes  only  a  few 
inches  deep ;  but  even  then  a  skilful  quarry  man  using  a  ball- 
drill  will  churn  down  a  small  hole  with  greater  rapidity  than 
a  one-hand  hammer  driller.  Almost  any  tyro,  however,  can 
drill  plug  holes  with  a  hammer  drill ;  but  it  takes  skill  to 
start  a  hole  with  a  ball-drill. 

For  deep  holes  in  soft  rocks,  like  shale,  a  churn-drill,  in 
the  hands  of  two  or  more  men,  is  the  best  hand  tool  in  use. 
By  building  a  light  staging  over  the  hole,  as  many  as  six  men 
may  operate  one  drill ;  three  men  on  the  ground  and  three 
on  the  staging;  but  this  is  seldom  done,  except  where  deep 
soundings  are  being  made  to  determine  the  nature  of  strata. 
For  breaking  up  shale  for  steam  shovel  work  holes  20  ft. 


METHODS  AND  COST  OF  HAND  DRILLING.          19 

deep  are  commonly  drilled.  A  pit  about  18  ins.  deep  and  "3 
ft.  in  diameter  is  often  dug  in  the  earth  overlying  the  rock, 
and  in  the  center  of  this  pit  the  drill  hole  is  started.  When 
the  hole  is  well  started  the  men  sit  on  the  sides  of  the  pit 
with  their  feet  in  the  bottom.  I  have  never  been  able  to  see 
the  philosophy  of  this  pit  digging,  for  a  circular  wooden  stool 
serves  as  well  as  the  ground  to  sit  on ;  and,  unlike  the  pit,  it 
can  be  used  over  and  over  again.  Moreover,  it  is  an  open 
question  whether  churn  drillers  should  be  permitted  to  sit 
down,  for  in  that  position  their  arms  and  shoulders  do  the 
entire  work,  whereas  when  standing  their  back  and  thigh 
muscles  aid  in  lifting  the  drill.  When  more  than  two  men 
are  operating  a  drill  it  is  practically  impossible  to  use  the 
back  and  thigh  muscles;  hence  the  efficiency  of  each  man 
is  greatly  reduced  when  a  third  man  takes  hold  of  the  drill, 
unless  the  third  man  stands  on  a  scaffolding  above  the  heads 
of  the  two  men  on  the  ground.  A  round  drill  rod  24  m-  m 
diameter  weighs  1.5  Ibs.  per  ft.  of  length;  a  I  in.  rod,  2.65 
Ibs. ;  a  1^4-in.  rod,  4.1  Ibs.  per  ft.,  and  a  il/2-m.  rod  5.95  Ibs. 
per  ft.  It  is  well  to  bear  these  weights  in  mind  when  con- 
sidering the  work  of  churn  drilling,  for  it  seems  such  a  little 
thing  to  add  only  %  in.  to  the  diameter  of  drill  stock,  while 
in  fact  the  addition  adds  greatly  to  the  work  of  lifting  the 
drill.  Up  to  a  certain  limit,  weight  is  desirable  in  drilling 
with  a  churn-drill;  for  the  drill  is  not  hurled,  but  allowed 
to  drop  freely  (unless  it  is  a  ball-drill),  and  does  its  work 
by  virtue  of  its  weight  and  velocity.  But  for  every  class  of 
rock  there  is  a  limit  to  the  weight  of  a  churn-drill  beyond 
which  there  is  an  actual  loss  of  efficiency,  due  to  the  greater 
number  of  drillers  required  to  lift  the  drill. 

Cost  of  Hammer  Drilling. — We  have  seen  that  the  diameter 
of  the  hole,  the  angle  at  which  the  hole  is  driven  and  the 
presence  or  absence  of  water  in  the  hole  all  affect  the  cost  of 
drilling  by  hand.  We  have  also  seen  that  the  method  of  drill- 
ing with  hammer-drills  or  with  churn-drills  is  an  important 
factor  in  the  cost.  Obviously  the  character  of  the  rock  is 


20          ROCK  EXCAVATION— METHODS  AND  COST. 

the  most  important  factor;  but  unfortunately  very  few  re- 
liable records  of  cost  of  drilling  in  different  kinds  of  rock  are 
to  be  found.  From  some  observations  on  hammer  drilling, 
with  a  il/2  in.  starting  bit  I  have  found  that  where  one  man 
is  holding  the  drill  vertically  and  two  men  are  striking,  the 
"ate  of  drilling  a  6- ft.  hole  is  as  follows : 

Ft.  in  Cost  per  ft., 

10  hrs.  cts. 

Granite  7  75 

Trap   (basalt)    1 1  48 

Limestone     16  33 

The  cost  is  based  upon  a  wage  rate  of  $1.75  per  Q-hr.  day 
per  man ;  and  does  not  include  the  cost  of  sharpening  drills, 
which  may  be  taken  at  5  to  8  cts,  per  ft.  more. 

I  have  found  that  a  man  drilling  plug  and  feather  holes  in 
granite,  each  hole  being  5/&  in.  diam.  by  2y2  in.  deep,  will 
average  one  hole  in  5  mins.,  including  the  time  of  cleaning 
out  holes,  and  the  driller  strikes  about  200  blows  in  drilling 
the  hole.  No  water  is  used  in  drilling  these  shallow  holes, 
for  the  dust  is  readily  and  quickly  cleaned  out  with  a  little 
wooden  spoon.  In  8  hrs.  of  steady  work  about  100  holes  can 
be  drilled,  which  is  about  21  ft.  of  5/£  in.  hole.  But  in  plug 
and  feather  work  part  of  the  time  is  spent  in  selecting  rock, 
driving  the  plugs,  etc.,  so  that  50  or  60  holes  drilled  and 
plugged  and  feathered  is  generally  counted  a  fair  day's  work. 

I  am  indebted  to  Mr.  John  B.  Hobson  for  the  following 
data  of  hammer  drilling  in  a  British  Columbia  mine :  Rock 
was  augite  diorite  and  firm  red  porphyry ;  starting  bit,  I  ^ 
ins. ;  finishing  bit,  i1/^  ins. ;  %  in.  steel ;  holes,  6  ft.  deep ;  8-lb. 
hammer.  Two  miners  (one  holding  drill  and  one  striking) 
averaged  14.8  ft.  per  lo-hr.  shift.  With  wages  at  $2  a  day 
the  cost  was  nearly  28  cts.  per  ft.  of  hole. 

Mr.  Frank  Nicholson  states  that  in  mining  chalcopyrite  in 
magnesian  limestone  at  St.  Genevieve,  Mo.,  a  day's  work 
for  a  striker  and  a  holder  was  12  ft.  of  hole  drilled.  The 


METHODS  AND  COST  OF  HAND  DRILLING.          21 

drills  had  i^-'m.  starting  bits,  %  in.  octagon  steel  being 
used.  Wages  in  1882  were  only  $1.35  for  miners  doing  this 
work,  the  shift  being  10  hrs.  long.  It  cost  $6.50  per  lin.  ft. 
to  drive  a  4  X  6  ft.  drift,  using  40  per  cent,  dynamite. 

In  driving  the  Hoosac  Railway  Tunnel  in  1865  (see 
Drinker)  through  gneiss  and  tough  mica  schist,  2-ft.  holes 
were  drilled  in  the  headings,  using  i^-in.  starting  bits,  anu 
each  driller  averaged  only  3^  ft.  of  hole  per  lo-hr.  shift. 
From  7  to  13  bits  were  dulled  in  drilling  each  hole.  Drilleia 
were  paid  $2.25  a  day.  Black  powder  was  used  in  blasting, 
which  accounts  for  the  fact  that  the  holes  were  large  in  di- 
ameter and  shallow. 

In  driving  the  Glasgow  water  works  tunnels  in  1856-1857 
(see  Simms),  through  very  hard  mica  schist,  drill  holes  20 
ins.  deep  and  i%  ins.  diam.  were  drilled,  a  new  bit  being  re- 
quired for  each  inch  of  hole.  The  time  required  to  drill  each 
hole  is  stated  to  have  been  ij^.  hrs.,  but  no  statement  is 
made  as  to  the  number  of  men  engaged — presumably  two  or 
three  on  each  hole. 

Ihlseng  states  that  Swedish  iron  miners  each  average  5  ft. 
of  hole  a  day  in  medium  rock ;  single-handed  drilling ;  holes 
2,y2  ft.  deep;  but  he  does  not  give  the  size  of  bits — a  serious 
omission. 

On  the  Nesquehoning  Railway  Tunnel  (Drinker)  driven 
in  1870  through  the  conglomerates  and  shales  of  Carbon 
county,  Pa.,  drillers  received  $2.25  and  laborers  $2  per  8-hr, 
shift.  The  cost  of  hand  drilling  was  56  cts.  per  ft.  of  hole, 
of  which  6  cts.  was  for  steel  and  sharpening.  Machine  drill- 
ing in  this  same  material  cost  14  cts.  per  ft.  of  hole,  including 
repairs  to  drills,  etc.,  but  not  including  interest  and  depre- 
ciation. 

In  excavating  hard  porphyry  for  the  rock-fill  dam  at  Otay, 
Cal.,  Mr.  W.  S.  Russell  states  that  a  good  day's  work  for 
three  men  drilling  (one  holding  and  two  striking)  was  6  to 
8  ft.  of  hole,  costing  about  80  cts.  per  ft.  of  hole  drilled.  The 
holes  were  drilled  20  ft.  deep  vertically  and  sprung.  This 


22         ROCK  EXCAVATION— METHODS  AND  COST. 

was  an  unusual  depth  of  hole  for  hammer  drilling,  and  ac- 
counts for  the  high  cost  per  foot.  It  shows  also  how  un- 
economic is  hammer  drilling  in  deep  vertical  holes  com- 
pared with  churn  drilling. 

In  driving  a  small  (3  X  4^-ft.)  tunnel  through  tough 
sandstone  one  driller  averaged  4  to  5  holes,  each  I  y2  ft.  deep, 
per  8-hr,  shift,  using  %  in.  bit  for  the  starter;  and,  upon 
cleaning  up,  the  advance  was  I  ft.  per  shift  for  one  man. 
Each  hole  was  charged  with  half  a  stick  of  75  per  cent,  dyna- 
mite. 

Cost  of  Churn  Drilling. — I  am  indebted  to  Mr.  W.  M. 
Douglass,  of  the  firm  of  Douglass  Bros.,  contractors,  for  the 
following  data  on  drilling  with  churn-drills,  for  railroad 
work  in  western  Ohio.  Three  drillers  were  used  for  putting 
down  the  first  18  ft.  of  hole  in  blue  sandstone  the  first  day 
(10  hrs.),  and  four  men  were  used  for  putting  down  the  last 
12  ft.  of  hole,  so  that  it  required  70  hrs.  of  labor  at  15  cts.  per 
hr.,  or  $10.50,  for  a  3O-ft.  hole,  making  the  cost  35  cts.  per 
ft.  In  brown  sandstone  it  required  70  to  80  hrs.  labor  to 
put  down  30  ft.  The  drill  holes  were  2^4  ins.  at  top  and  1^2 
ins.  at  bottom.  Drilling  with  steam  drills  in  this  same  stone, 
holes  20  ft.  deep,  cost  12  cts.  per  ft.,  including  everything 
except  interest,  depreciation  and  drill  sharpening.  The  cost 
of  hand  drilling  agrees  very  closely  with  my  own  records 
of  similar  work  in  Pennsylvania. 

Trautwine  gives  the  following  rates  of  drilling  3-ft.  ver- 
tical holes,  starting  with  a  i^4-in.  bit,  one  man  drilling  with 
a  churn-drill,  shift  10  hrs.  long: 

Solid  quartz   4     ft.  in  10  hrs. 

Tough  hornblend 6     "    "  " 

Granite  or  gneiss 7.5  "    "  " 

Limestone   8.5  "    "  "     " 

Sandstone   9.5  "    "  "     " 

It  should  be  observed  that  the  holes  in  this  case  are  shallow 
(3  ft.),  and  the  diameter  (i%  ins.)  is  large  for  such  shallow 


METHODS  AND  COST  OF  HAND  DRILLING.          23 

holes,  indicating  that  Trautwine's  data  applied  to  rock  exca- 
vation where  black  powder  was  used. 

Hand-Drill  Bits. — A  bit  has  least  work  to  perform  at  its 
center  (contrary  to  Drinker's  statements),  and  this  is  well 
shown  by  the  fact  that  a  bit  wears  most  rapidly  on  its  pro- 
jecting ears.  The  rock  near  the  center  of  the  hole  is  struck 
oftener  than  anywhere  else;  hence  it  is  quickly  cut  away; 
whereas  the  rock  near  the  circumference  of  the  hole  is  not 
struck  so  often  and  is  more  slowly  cut  or  crushed  to  pieces. 
The  ears  of  the  bit  may  project  considerably  beyond  the 
stock  of  the  drill  rod  when  the  rock  is  soft,  because  they 
wear  less  rapidly  and  resist  breaking  off  better  than  in  tough, 
hard  rock.  The  width  of  the  bit  may  be  30  per  cent,  to  100 
per  cent,  greater  than  the  diameter  of  the  drill  rod,  depend- 
ing upon  the  hardness  of  the  rock. 

For  one-hand  hammer  drilling  an  octagon  steel  rod  Y^  to 
fa  in.  in  diameter  is  commonly  used ;  but  ^  in.  to  I  in.  steel 
may  be  said  to  be  the  limits  of  size  used  for  one-hand  drill- 
ing. In  comparatively  soft  rock  a  jHi  m-  octagon  bar  may 
have  a  I  in.  bit,  a  %  in.  bar,  a  i%-in.  bit;  and  a  i^-in.  bar, 
a  3-in.  bit,  the  larger  sizes  of  bits  being  used  only  in  two- 
hand  hammer  drilling  or  churn  drilling.  In  two-hand  ham- 
mer drilling  a  1^4  to  i*/2-in.  hole  for  a  starter  in  medium 
hard  rock  that  is  to  be  drilled  to  depths  of  6  or  8  ft.  is  com- 
mon ;  for  it  must  be  remembered  that  as  the  hole  grows 
deeper  it  grows  smaller  in  diameter,  due  to  the  continuous 
wear  on  the  ears  of  the  bits,  so  that  unless  a  reamer  were 
used  it  would  be  impossible  to  have  a  uniform  diameter  of 
hole  except  in  very  soft  rock. 

The  least  admissible  diameter  of  hole  at  the  bottom  is 
about  24  in.,  where  dynamite  is  used.  In  the  days  of  black 
powder  a  much  larger  hole  was  necessary  in  order  to  hold 
enough  explosive,  although  it  cost  more  money  to  drill  the 
hole;  thus  in  the  Hoosac  Tunnel  the  holes  were  only  2  ft. 
deep  and  i^  ins.  in  diameter  at  the  mouth  of  the  hole.  It  is 
a  hard  rock  that  will  wear  the  ears  of  the  bit  so  fast  as  to 


24          ROCK  EXCAVATION— METHODS  AND  COST. 

reduce  the  diameter  of  the  hole  ^  in.  in  drilling  2  ft.,  so  that 
a  hole  6  ft.  deep  need  not  have  a  diameter  at  the  mouth  more 
than  24  m-  greater  than  at  the  bottom  even  in  very  hard  rock. 
The  chisel  edge  of  a  bit  is  ordinarily  made  not  straight 
across,  but  slightly  curved.  Different  authorities  have  as- 
signed different  reasons  for  giving  this  curvature  to  a  bit. 
Drinker  says  that  in  hard  rock  the  curve  must  be  quite  flat, 
but  in  soft  rock  it  must  be  very  rounding;  and  his  reason 
is  that  the  wear  of  the  bit  being  greatest  at  the  center  per- 
mits of  a  more  rounding  form  for  soft  rock.  As  a  matter  of 
fact  the  wear  is  never  greatest  at  the  center  of  a  bit,  and  in 
any  case  his  inference  is  illogical.  Aitken  says  that  the  bit 
is  made  rounding  so  as  to  give  greater  strength  to  the  ears, 
and  following  this  reason  to  its  logical  conclusion  would  give 
us  a  very  rounding  bit  for  very  hard  rock — precisely  the  op- 
posite of  the  form  recommended  by  Drinker.  To  me  it  seems 
apparent  that  a  rounded  cutting  edge  is  especially  desirable 
in  starting  a  hand-drilled  hole,  for  it  insures  effectiveness 
of  the 'first  few  blows  by  concentrating  the  work  upon  a 
small  area.  Moreover,  for  the  first  few  inches  of  the  hole, 
a  rounded  cutting  edge  is  desirable  because  any  slight  tilting 
of  the  drill  will  not  mean  the  concentration  of  the  energy  of 
the  blow  upon  one  of  the  ears,  which  is  the  weakest  part  of 
the  drill  and  most  easily  broken.  In  machine  drilling  this 
is  not  important,  but  in  hand  drilling  it  certainly  cannot  be 
overlooked.  As  corroborating  this  theory  it  should  be  noted 
that  the  short  drills  used  for  drilling  plug  and  feather  holes 
in  granite  are  invariably  made  very  rounding  or  convex; 
whereas  in  drilling  deep  holes  in  sandstone  consisting  of 
coarse  grains  poorly  cemented  together,  a  perfectly  straight- 
edged  drill  is  common.  A  rounded  or  convex  bit  cuts  a 
cup-like  bottom  in  the  drill  hole,  which  aids  in  keeping  the 
drill  centered ;  and  it  is  not  improbable  that  the  cup  acts  like 
a  mortar  in  which  the  chips  from  the  edges  of  the  hole  col- 
lect at  the  center  and  are  more  quickly  pulverized.  The  col- 
lecting of  chips  at  the  center  of  this  stone  mortar  gives  the 


METHODS  AND  COST  OF  HAND  DRILLING.          25 

bit  more  work  to  do  at  its  center,  which  is  precisely  what 
should  be  done  in  view  of  the  fact  that  the  outer  edges  would 
otherwise  have  most  of  the  work  to  do. 

The  wedge-shaped  edge  of  a  bit  is  made  as  sharp  as  will 
hold  up  without  rapid  dulling  or  chipping.  In  hard  rock 
the  bit  is  made  thick  near  the  edge,  and  with  angle  of  nearly 
90°.  In  soft  rock  the  bit  is  thin  and  sharp,  with  an  angle  of 
about  45°  between  the  faces.  To  this  rule  there  is  an  excep- 
tion, for  where  the  rock  is  a  sandstone  of  rather  coarse  grains 
poorly  cemented  together,  a  bit  that  has  a  blunt  edge  works 
fastest.  This  is  due  to  the  fact  that  the  grains  of  poorly 
cemented  stone  are  easily  broken  apart  and  then  the  blunt 
edge  crushes  them  quickly  like  a  pestle  in  a  mortar.'  A  blunt 
bit  is  used  in  drilling  small  holes  in  earth,  but  for  a  different 
reason ;  the  blunt  bit  in  earth  compacts  the  earth  and  crowds 
it  aside,  'necessitating  less  cleaning  out  of  the  hole. 


'Fig.  i. 

Machine  Drill  Bits. — We  have  thus  far  considered  only  the 
plain  chisel  bit,  which  is  the  type  commonly  used  in  hand 
drilling.  In  machine  drilling  a  cross  (or  square)  bit  (  +  ), 
or  an  ex  (X)  bit,  is  commonly  used.  Occasionally  a  Z  bit 
is  seen.  These  bits  possess  the  advantage  of  drilling  a  more 
truly  circular  hole  than  a  chisel  bit  ever  does. 

Fig.  i,  from  an  article  by  T.  H.  Proske,  in  the  Engineering 
and  Mining  Journal  May  5,  1904,  shows  shapes  of  machine 
drill  bits  used  in  the  United  States.  Bit  "A"  is  the  common 
cros5  (_(_)  bit,  and  bit  "D"  is  the  X-bit.  The  theoretical 


26          ROCK  EXCAVATION— METHODS  AND  COST. 

advantage  of  the  X-bit  lies  in  the  fact  that  its  cutting  edges, 
aa  and  bb,  are  not  perpendicular  to  one  another,  as  they  are 
in  the  +-bit,  so  that  they  do  not  strike  twice  in  the  same 
place  in  making  one  complete  revolution ;  for  the  bit  is  turned 
y&  revolution  during  each  up  stroke.  Bits  "E"  to  "H"  are 
hand-sharpened  -| — bits,  which  usually  have  curved  cutting 
edges,  instead  of  the  straight  edges  of  machine-sharpened 
bits.  Bit  "B"  is  the  Fitch  bit,  which  has  proved  very  efficient 
in  the  extremely  hard  jaspar  of  the  Champion  Mine,  Mich- 
gan ;  tests  with  a  2^-in.  Rand  drill,  under  60  Ibs.  air  pres- 
sure, having  shown  an  average  drilling  speed  of  0.28  in.  per 
min.  for  the  -| — bit,  as  compared  with  0.66  in.  per  min.  with 
the  Fitch  bit.  Bit  "C"  is  the  Brunton  bit,  invented  by  D.  W. 
Brunton,  used  by  the  Anaconda  Copper  Co.,  Butte,  Mont., 
and  at  a  number  of  other  mines  in  Montana  and  Idaho.  With 
this  bit  the  drill  piston  must  turn  half  way  around  before  the 
cutting  edges  strike  twice  in  the  same  place. 

A  bit  should  "mud"  freely,  and  to  do  this  the  faces  form- 
ing the  chisel  edge  should  meet  at  an  angle  of  about  80°  for 
soft  rock  and  90°  for  hard  rock.  A  flat  chisel  edge,  like  bit 
"G,"  or  a  sharp  edge,  like  bit  "H,"  will  not  mud  freely. 

Bit  "E"  is  the  common  hand-sharpened  cross-bit;  bit  "F" 
is  the  same  after  one-half  the  originally  forged  cross  has 
worn  off;  bit  "G"  shows  the  cross  nearly  worn  off;  bit  UH" 
is  the  work  of  a  careless  blacksmith,  the  corners  being  drawn 
out  and  the  center  not  set  back. 

Sharpening  Hand  Drills. — A  good  blacksmith  is  as  es- 
sential to  economic  rock  excavation  as  good  hand  drillers. 
For  this  reason  every  contractor  and  every  mine  manager 
having  charge  of  drilling  operations  should  know  at  sight  a 
good  blacksmith  when  he  sees  him  do  his  work.  To  be  able 
to  do  this  it  is  not  necessary  to  become  a  blacksmith,  but 
simply  to  learn  the  art  of  drill  sharpening  by  reading  and 
by  watching  and  by  inquiry.  One  of  the  best  foremen  of 
rock  excavation  that  I  know  is  a  cripple  who  has  never  done 
a  stroke  of  drilling  or  tool  sharpening  himself ;  but  he  knows 


METHODS  AND  COST  OF  HAND  DRILLING.          27 

exactly  how  it  should  be  done  and  cannot  be  imposed  upon 
by  a  pretender.  The  educated  man  is  apt  to  be  fearful  of 
showing  himself  ignorant  of  practical  work  by  inquiring 
into  the  methods  of  the  drill  sharpener. 

To  begin  with  the  blacksmith  must  have  good  drill  steel 
(not  tool  steel)  to  work  with.  Drill  steel  contains  0.8  to  i 
per  cent,  of  carbon.  If  the  steel  loses  any  of  this  carbon  by 
oxidation  it  becomes  softer  and  dulls  quickly.  In  heating 
the  bit  it  is  therefore  essential :  ( I )  That  the  heating  be  not 
too  long  continued,  nor  carried  above  a  cherry  red;  (2)  that 
the  air  blast  be  not  too  strong;  (3)  that  the  bit  and  some 
of  the  shank  be  well  bedded  in  the  coal  or  charcoal  and  not 
in  a  thin  bed  of  hot  cinders.  If  these  rules  are  not  carefully 
followed  the  steel  will  be  "burned,"  which  means  simply  that 
some  of  the  steel  will  be  oxidized  and  that  this  oxide  will  in 
turn  oxidize  some  of  the  carbon  of  the  steel.  The  heating 
should  be  uniform,  and  to  secure  uniformity  the  blacksmith 
turns  the  drill  over  in  the  fire.  When  the  bit  has  become  a 
dull  cherry  red  it  should  be  removed  with  as  little  delay  as 
possible  and  dressed.  If  the  corners  of  the  bit  are  badly 
worn  the  chisel  edge  must  first  be  upset  (blunted)  to  give 
the  proper  width;  then  the  drill  is  held  on  the  anvil  at  a 
slope  of  about  I  ft.  rise  to  2  ft.  horizontal,  the  edge  of  the 
bit  being  even  with  the  edge  of  the  anvil.  In  this  posi- 
tion it  is  hammered,  turning  over  at  intervals,  until  a  new 
cutting  edge  is  made.  A  file  may  be  used  (while  the  bit  is  still 
hot)  for  the  final  shaping.  If  the  drill  is  simply  dull  it  is  not 
necessary  to  upset  it,  but  when  taken  from  the  fire  it  is  tapped 
or  brushed  to  remove  any  cinders,  laid  on  the  anvil  and 
struck  with  light  glancing  blows  until  an  edge  has  been 
formed.  The  blows  should  be  glancing  so  as  to  draw  the 
steel  fibres  toward  the  cutting  edge,  and  the  lighter  the  blows 
that  will  accomplish  this  result  the  tougher  the  steel  becomes. 
The  width  of  each  bit  should  be  carefully  gaged,  for  noth- 
ing is  more  exasperating  to  the  drillers  than  to  have  a  care- 
less blacksmith  send  out  bits  irregular  in  width  from  ear  to 


28          ROCK  EXCAVATION— METHODS  AND  COST. 

ear.  As  above  stated,  each  longer  set  of  drills  must  have 
a  slightly  smaller  bit,  for  all  drill  holes  grow  narrower  as 
they  grow  deeper.  The  exact  reduction  in  size  depends  upon 
the  hardness  of  the  rock,  and  is  ascertained  by  experiment. 
The  bit  after  being  shaped  must  be  reheated  for  tempering. 
The  heating  is  done  in  the  forge,  as  before,  until  the  bit  is 
cherry  red,  when  it  is  immediately  plunged  into  water  for 
a  moment  to  partly  cool  it,  and  then  rubbed  on  a  stone  to 
remove  the  scale,  so  that  the  play  of  colors  may  be  readily 
seen  in  a  dark  corner  of  the  shop.  The  colors  indicate  ap- 
proximately the  following  temperatures : 

Very  Pale  yellow 43°°F 

Straw    : 470° 

Brown    490° 

Purple • 530° 

Full  blue 560° 

Dark  blue 600° 

As  the  drill  cools  the  colors  should  advance  parallel  to  the 
cutting  edge  if  the  cooling  is  uniform ;  if  otherwise,  that  side 
of  the  bit  on  which  the  colors  are  advancing  most  rapidly 
should  be  held  in  water.  This  plunging  into  the  water  is 
sometimes  repeated  several  times  before  the  colors  move 
parallel  with  the  edge  of  the  bit.  Finally,  when  the  colors 
move  parallel  with  the  edge,  watch  the  edge  closely  until  it 
is  straw  color  and  plunge  into  water  a  short  distance,  waving 
it  back  and  forth  (to  insure  rapid  cooling)  until  the  steam 
ceases  to  form;  then  leave  it  in  the  quenching  bath.  The 
quenching  bath  should  be  a  tub  large  enough  to  cool  the 
drills  without  raising  the  temperature  of  the  water  sensibly. 
Some  of  the  baths  commonly  used  are  brine,  water,  rape- 
seed  oil,  tallow  and  coal  tar ;  the  brine  cooling  the  drill  fast- 
est and  the  coal  tar  slowest. 

Sharpening  Machine  Drills. — The  ordinary  -f  or  X  bit 
used  in  machine  drills  usually  receives  treatment  somewhat 


METHODS  AND  COST  OF  HAND  DRILLING. 


29 


different  from  that  just  described,  partly  due  to  its  shape 
and  partly  due  to  the  greater  mass  of  metal  in  the  bit.    The 


Fig.  2. 


Fig.  3- 


bit  is  first  shaped  by  a  special  set  of  blacksmiths'  tools, 
shown  in  Fig.  2  (from  Ingersoll  catalogue)  consisting  of 
a  "dolly,"  A,  "sow,"  B;  "spreader,"  C;  "flatter,"  D;  and 
"swage,"  E.  The  best  blacksmith  that  I  have  had  makes  a 
"dolly"  for  each  size  of  bit.  To  do  this  he  heats  a  block  of 
steel,  and  drives  against  it  a  cold  drill  bit  of  the  exact  shape 
and  gage  desired,  thus  producing  what  he  terms  a  "female 
bit,"  which  is  afterward  tempered  hard.  The  "female  bits," 
or  dies,  of  different  sizes  are  fastened  to  the  anvil  so  that 
a  hot  bit  which  is  to  be  shaped  can  be  held  horizontally  and 
hammered  into  the  die.  The  result  is  that  all  bits  are  rapid- 
ly made  true  to  gage  and  well  shaped.  After  shaping  the 
bit  is  reheated  for  tempering,  and  at  the  proper  temperature 
is  placed  in  the  cooling  bath.  Fig.  3  shows  a  cooling  bath 
(after  T.  H.  Proske),  in  which  a  grate  or  screen  is  placed 
Y^  in.  below  the  water  surface  to  support  the  bit  until  it  is 
cool.  A  rack  built  around  the  tank,  with  nails  3  ins.  apart, 
holds  the  drills  upright.  The  hot  steel  above  the  water  line 
prevents  the  chill  from  reaching  up  to  the  water  line,  so  that 
only  the  face  of  the  bit  is  hardened.  The  mass  of  metal  in 
the  bit  and  the  fact  that  at  each  resharpening  the  water  line 
is  higher  up  on  the  drill  (due  to  wear  of  bit)  eliminate 
danger  of  cracking  at  the  water  line.  When  this  method  of 


30          ROCK  EXCAVATION— METHODS  AND  COST. 

cooling  is  used  the  edges  of  the  bit  should  be  perfectly 
straight  and  not  rounding.  A  bit  immersed  for  a  short  time, 
and  then  withdrawn  for  annealing,  is  apt  to  be  soft  centered, 
due  to  the  fact  that  the  center  cools  more  slowly  than  the 
corners. 

Within  the  last  few  years  machines  for  sharpening  drills 
have  come  into  use  in  some  of  the  large  mines.  I  have  rec- 
ords of  the  work  done  by  two  types  of  machine-drill  sharp- 
eners: The  "Ajax"  and  the  "Word,"  which  consist  essen- 
tially of  two  air-driven  hammers,  one  hammer  working  hori- 
zontally, the  other  working  vertically.  Mr.  Robert  A.  Kin- 
zie  informs  me  that  the  Alaska  Treadwell  mines  use  Ajax 
drill  sharpeners,  and  that  one  machine  sharpens  460  bits  per 
shift.  The  first  Word  drill  sharpeners  were  used  at  the 
Franklin  copper  mine,  near  Houghton,  Mich.,  and  at  the 
Black  Oak  mine,  Loulsbyville,  Cal.  Mr.  W.  G.  Scott,  super- 
intendent of  the  Black  Oak  mine,  is  quoted  in  the  Mining 
and  Scientific  Press,  April  n,  1904,  as  follows: 

"The  machine  ran  183  days  with  nominal  repairs.  Aver- 
age hours  run  daily,  4 ;  total,  732  hours.  One  man  operated 
the  drill,  attended  his  own  forge  and  made  necessary  re- 
pairs. Any  man  who  can  set  up  and  run  a  machine  drill 
can  run  the  drill  sharpener.  Approximate  number  of  drills 
upset  and  sharpened,  36,000;  average,  50  drills  per  hour. 
Fuel  used  is  less  than  one-half  that  required  in  hand  work. 
One  and  one-half  minutes  are  required  to  form  and  sharpen 
a  new  drill.  Over  60  drills  have  been  repointed  by  this  ma- 
chine in  one  hour.  The  life  of  a  bit  sharpened  by  this  drill 
is  longer  than  when  done  by  hand,  the  bits  being  better 
formed  and  more  compact,  taking  a  better  and  more  even 
temper.  The  different-sized  points  are  made  with  uniform- 
ity. By  a  change  in  the  dies  the  machine  will  sharpen  hand 
drills.  Before  we  used  this  machine  we  employed  two  drill- 
sharpening  blacksmiths  and  two  helpers  to  make  and  sharp- 
en drills.  The  saving  of  the  machine  over  hand  labor  in 
six  months  has  been  $1,738.50;  saving  on  coal  (183  days), 
$183;  or  a  total  saving  for  six  months  of  $1,921.50." 


CHAPTER  III. 
MACHINE    DRILLS    AND   THEIR    USE. 

Machine  Drill  Mechanism. — To  discuss  the  mechanical  de- 
tails of  rock-drill  construction  is  not  within  the  scope  of  this 
chapter,  for  to  do  so  adequately  would  require  a  book  in  it- 
self. Moreover,  a  careful  study  of  the  line-cuts  and  descrip- 
tive matter  of  catalogues,  supplemented  by  some  machine- 
shop  experience  where  drills  are  repaired,  is  indispensable 
to  any  one  who  wishes  thoroughly  to  acquaint  himself  with 
rock-drill  mechanism.  I  shall  therefore  confine  myself  to  an 
enumeration  of  the  parts  and  their  functions,  referring  to 
Fig.  4,  page  33,  which  is  a  section  of  one  of  the  standard 
makes. 

1.  The  cylinder. 

2.  Front  head  of  the  cylinder  and  stuffing  box  through  which  the 
piston  works. 

3.  Back  head  of  the  cylinder. 

4.  One  of  the  two  side-rods  or  "through-bolts"  that  hold  the  cyl- 
inder heads  in  place. 

5.  Steam  chest. 

6.  Spool  valve. 

7.  Tappet  valve  which  is  oscillated  by  the  shoulders  on  the  piston. 

8.  The  piston.     Note  the  grooves  near  its  ends  for  the  cylinder 
rings  which  make  an  air-tight  fit. 

9.  The  chuck  at  the  end  of  the  piston  rod  for  holding  the  shank 
of  the  drill  steel. 

10.  The  rifle  bar  for  rotating  the  piston  on  each  back  stroke. 

11.  Key  that  aids  in  holding  the  shank  of  the  drill  steel. 

12.  The  U-shaped  chuck  bolt  with  a  nut  at  each  end  of  the  U. 

13.  Two  pawls  forced  by  two  pawl  springs  to  catch  the  teeth  of 
the  ratchet  wheel. 

14.  The  ratchet  wheel  which  prevents  the  rifle  bar  (10)   turning 
on  the  forward  stroke  of  the  piston,  but  allows  it  to  turn  on  the 
back  stroke. 

15.  The  guide  shell  on  which  the  cylinder  is  mounted. 

16.  The  cup  by  which  the  guide  shell  is  fastened  to  the  tripad  or 
column  arm. 

31 


32          ROCK  EXCAVATION—METHODS  AND  COST. 

17.  Feed  nut  fastened  to  the  cylinder. 

18.  Feed  screw  for  moving  the  cylinder  along  the  guide  shell. 

19.  Crank  of  feed  screw. 

Air  drills  of  the  rotary  type  are  still  in  use  in  Europe ;  but 
in  America,  which  is  the  birthplace  of  the  air  drill,  no  type 
is  in  use  for  rock  drilling  but  the  percussive  type.  The  drill 
is  churned  back  and  forth  in  the  hole  by  compressed  air  or 
steam  power,  and  after  each  stroke  it  is  mechanically  turned 
a  fraction  of  a  circle.  The  drill  is  fed  forward  by  hand,  a 
crank  at  the  end  of  a  feed-screw  being  used  for  this  pur- 
pose. A  longer  drill  is  inserted  every  2  ft.  in  depth  of  hole, 
for  2  ft.  is  the  limit  of  feed  of  the  ordinary  feed  screw  used. 
Automatic  feed  devices  are  not  commonly  used  on  drills  of 
ordinary  sizes,  but  only  on  very  large  drills  for  submarine 
work. 

Sizes  of  Air  Drills. — The  size  of  an  air  drill  is  denoted  by 
the  inner  diameter  of  its  air  or  steam  cylinder;  thus  a  3^- 
in.  air  drill  is  one  having  a  cylinder  3^  ms.  diam. 

The  smallest  size,  2*4-in.  drill,  is  called  a  "baby  drill," 
or  a  one-man  drill — the  latter  name  being  given  to  the  drill 
because  it  can  be  readily  moved  about  and  set  up  by  one 
man.  For  narrow  work  in  mines  the  baby  drill  is  adapted. 
It  is  also  used  largely  for  drilling  plug  and  feather  holes, 
and  might  often  be  used  profitably  for  shallow  cuts  and 
trenches.  The  sizes  most  commonly  used  for  general  con- 
tract work,  tunneling  and  mining  are  the  3^-in.  and  the 
3^4-in.  drills.  A  recent  report  states  that  in  101  gold  mines 
of  the  Transvaal,  South  Africa,  2,355  ^r  drills  are  in  use, 
and  of  this  number  1,680,  or  70  per  cent,  are  3^4-in.  drills. 
Where  the  holes  are  deep  and  the  drilling  hard,  it  is  often 
found  that  the  3^g-in.  drill  is  the  size  to  be  chosen.  Thus, 
in  shaft  sinking  in  syenite  at  the  Treadwell  Mine,  Alaska, 
it  has  been  found  that  the  number  of  feet  drilled  with  the 
3^-in.  drill  is  fully  30  per  cent,  greater  than  with  the  3%- 
in.  drill.  As  we  proceed  it  will  become  more  and  more  ap- 
parent that  the  most  economic  size  of  drill  for  any  particular 


MACHINE  DRILLS  AND  THEIR   USE. 


33 


34 


ROCK  EXCAVATION—  METHODS  AND  COST. 


class  of  work  can  only  be  determined  by  experiment,  and 
that  as  yet  no  hard  and  fast  rules  can  be  laid  down.  The  fol- 
lowing table  gives  approximately  the  principal  data  regard- 
ing air  drills  : 


Diameter    of    cylin- 

der      ins. 

2/4 

2L£ 

234 

3l/S 

3^4 

3*6 

Length  of  stroke,  ins. 

5 

6 

6*/2 

iff 

7% 

Length  of  drill  from 

end    of    crank    to 

end  of  piston,  ins. 

36 

43 

50 

50 

50 

52 

Depth  of  hole  drill- 

ed without  change 

of  bit   ins. 

15 

20 

24 

24 

24 

24 

Diameter    of    supply 
inlet     (standard 

pipe)     ins. 

•y. 

•y. 

34 

i 

i 

1  14 

Approximate  strokes 

per    minute     with 

60  Ibs.  pressure  at 

drill     

500 

450 

375 

350 

325 

300 

Depth      of     vertical 

hole  each  machine 

will  drill  easily,  ft. 
Diameter     of     holes 

6 

8 

10 

14 

16 

20 

drilled   as    desired 

from     ins. 

34   tO   ll/2 

i  to  iYi 

l*/2  to  2  J4 

iy2io2y4 

1  34  to  234 

i34  to  3 

Diameter  of  octagon 

steel   used    .  .  ins. 

34  to  ^ 

H  to  i 

i  to  ij4 

il/&  to  ij4 

1  1A  to  1  54 

i  %-ifa 

Best    size    of    boiler 

to   give   plenty   of 

steam     at     high 

pressure   

6H.  P. 

8H.  P. 

8H.  P. 

9-H.  P. 

10  H.  P. 

12  H.  P. 

Best   size  of   supply 

pipe     to     carry 

steam    100   to   200 

feet  ins. 

* 

34 

y* 

i 

i 

154 

Drill     unmounted 

with  wrenches 

and     fittings,     not 

boxed    Ibs. 

128 

190 

265 

3i5 

285 

390 

Tripod      without 

weights,    not    box- 

ed    Ibs. 

80 

1  60 

1  60 

160 

210 

275 

Holding    down 

weights,    not    box- 

ed    Ibs. 

120 

270 

270 

285 

330 

375 

Drill,  tripod,  weights 

and  wrenches, 

boxed    Ibs. 

415 

660 

820 

885 

952 

1230 

Drill     unmounted 

with  wrenches  and 

fittings  without  tri- 
pod  or   column.  .  . 
Tripod  and  weights 

$I7O.OO 
$30.00 

$200.00 
$50.00 

$225.00 
$50.00 

$250.00 

$50.00 

$275.00 

$50.00 

$295.00 

$55-00 

Handling  a  Drill  on  a  Tripod.  —  A  drill  mounted  upon  a 
tripod  is  the  combination  commonly  used  for  surface  drill- 
ing, and  even  underground  on  the  benches  of  railway  tun- 
nels and  often  in  stoping  ores.  I  shall  discuss  the  handling 
of  the  tripod  drill  somewhat  in  detail,  for  every  manager  of 
drilling  forces  should  know  such  of  the  details  as  will  be 


MACHINE  DRILLS  AND  THEIR   USE.  35 

set  forth,  beside  many  others  which  the  recital  of  these  de- 
tails may  stimulate  him  to  learn  for  himself  by  observation. 
The  order  of  tripod  drilling  operations  is  as  follows : 

1.  Have  laborers  clean  away  all  earth  and  loose  rock  over 
the  sites  of  proposed  drill  holes;  for  earth  would  clog  the 
drill  and  would  not  give  a  stable  support  for  the  tripod.    If 
the  surface  of  the  rock  to  be  drilled  is  loose  and  shelly,  have 
the  laborers  clean  it  away  down  to  solid  rock,  for  a  hole  can- 
not be  started  on  loose,  shelly  rock.     I  have  often  seen  the 
expensive  drill  crew  delayed  15  or  20  minutes  while  one  of 
the  crew  was  occupied  cleaning  away  shelly  rock.   A  laborer 
at  15  cts.  an  hour  will  do  this  work  as  well  as  a  drill  crew  at 
50  cts.  an  hour. 

2.  Set  the  tripod  over  the  site  of  the  proposed  hole,  giving 
the  legs  a  good  spread  to  secure  stability.    At  best  there  is 
considerable  vibration  when  the  drill  is  at  work.     A  small 
"cat  hole"  is  dug  in  the  rock  with  a  pick  or  a  hand  drill  for 
the  point  of  each  tripod  leg  to  set  in. 

3.  Having  "spotted"  the  leg  points,  the  legs  are  adjusted 
until  the  saddle  is  about  horizontal.    The  set  screws  are  then 
tightened  and  the  tripod  leg  weights  put  on. 

4.  If  the  machine  is  not  already  in  its  saddle,  place  it  there 
and  fasten  the  saddle  to  the  cup. 

5.  Unloosen  the  nut  that  clamps  the  tripod  saddle  and 
point  the  drill  in  the  line  of  the  proposed  hole. 

6.  The  "starter,"  or  first  drill,  is  inserted  in  the  chuck  af- 
ter wiping  the  shank  of  the  drill  clean ;  and  the  nuts  of  the 
chuck  bolts  are  set  by  first  screwing  one  and  then  the  other 
until  they  are  perfectly  tight.    Be  sure  that  the  shank  of  the 
drill  is  in  as  far  as  it  will  go  before  tightening  the  U-bolt. 
The  starter  should  have  a  sharp  bit  welded  to  a  full  sized 
and  perfectly  straight  drill  rod.     Beware  of  a  slender  drill 
rod  with  a  nub  bit  wherever  difficulty  is  expected  in  starting 
the  hole. 

7.  The  piston  is  drawn  back  until  it  strikes  the  cylinder 
head. 


36          ROCK  EXCAVATION— METHODS  AND  COST, 

The  bit  is  fed  forward  until  the  bit  strikes  the  rock,  and 
the  point  where  it  strikes  is  spotted. 

9.  The  piston  is  shoved  into  the  cylinder,  and  the  bit  is 
raised  by  the  feed-screw. 

10.  The  rock  where  the  bit  will  strike  is  faced  square  for 
an  area  of  y2  in.  or  more  larger  than  the  bit ;  for  if  the  drill 
strikes  a  glancing  blow  it  may  bend  the  shank,  and  due  to 
the  vibration  of  the  machine,  it  will  vary  y2  in.  in  its  align- 
ment. 

11.  The  piston  is  moved  in  until  it  is  about  the  center  of 
the  cylinder,  and  a  little  oil  is  let  into  the  cylinder  if  the 
machine  has  not  been  used  in  some  time,  and  is  operated 
by  air. 

12.  Turn  the  air  or  steam  through  the  hose  before  coup- 
ling it  to  the  drill,  in  order  to  blow  out  any  dust  or  chips ; 
turn  off  the  air  and  wipe  the  threads  of  the  coupling  clean. 

13.  Turn  off  the  throttle  valve  of  the  machine,  then  couple 
on  the  hose. 

14.  Let  the  drill  runner  test  all  the  nuts  with  his  wrench ; 
and  in  tightening  nuts  bear  down  on  the  wrench  instead  of 
pulling  up,  as  pulling  up  may  shift  the  machine. 

15.  Run  the  bit  down  to  within  I  in.  of  the  rock,  for  in 
that  position  the  drill  automatically  gives  a  short  stroke,  and 
a  short  stroke  is  always  desirable  in  starting  a  hole. 

16.  Open  and  then  close  the  throttle  if  steam  is  the  power 
used,  and  work  the  piston  back  and  forth  by  hand  two  or 
three  times,  so  as  to  heat  everything  up  evenly  and  prevent 
breaking  of  a  part.     Then  tighten  up  the  side  rods  which 
have  been  left  loose  to  avoid  breaking  them  by  the  heat  ex- 
pansion.    Tighten  them  evenly  and  no  more  than  is  neces- 
sary to  secure  a  tight  steam  joint. 

17.  Open  the  throttle  valve  part  way  so  that  the  drill  will 
strike  a  light  blow  until  a  depth  of  hole  has  been  reached 
that  is  greater  than  the  full  stroke  of  the  drill,  that  is,  until 
the  bit  no  longer  lifts  above  the  surface  of  the  rock.    A  little 
slowness  in  starting  is  time  saved,  because  the  danger  of 


MACHINE  DRILLS  AND   THEIR   USE.  37 

breaking  the  drill  is  avoided  and  a  true  round  hole  is  secured. 

1 8.  The  helper  "tends  chuck"  by  pouring  in  water,  using 
a  can  filled  from  a  bucket  nearby. 

19.  When  the  drill  has  worked  up    to    its    full    stroke 
(6  ins.)  the  feed-crank  is  turned  slowly  so  as  to  keep  the 
bit  in  position  to  strike  a  full  blow.    If  the  feed  is  too  slow 
the  piston  strikes  the  cylinder  head  with  a  metallic  sound 
that  is  unmistakable;  in  which  case  give  the  feed-crank  a 
few  rapid  turns  to  prevent  damage.     If  the  feed  is  too  fast 
the  stroke  is  automatically  shortened,  and  the  rate  of  pene- 
tration of  the  drill  is  materially  decreased. 

20.  When  steam  is  used  instead  of  air,  more  or  less  steam 
will  condense  in  the  feed  pipe  during  the  time  that  a  drill 
is  being  moved  from  hole  to  hole.    Therefore  do  not  let  oil 
into  the  cylinder  until  the  drill  has  been  running  some  time 
(long  enough  for  the  water  to  have  all  been  blown  out).  The 
piston  must  be  kept  perfectly  lubricated  to  avoid  rapid  wear. 

21.  When  the  feed-screw  has  reached  its  limit  (the  feed 
is  2  ft.  in  ordinary  sizes),  the  air  is  turned  off;  the  drill  is 
raised  as  far  as  the  feed  screw  will  run,  and  taken  out  of 
the  chuck.    The  hole  is  cleaned  with  a  "gun"  or  sand  pump. 
If  the  hole  is  shallow  a  stick  broomed  at  the  end  may  be  used 
to  remove  the  sludge  at  the  bottom  of  the  hole. 

These  twenty-one  rules  of  ordinary  procedure  may  now 
be  supplemented  by  a  few  rules  for  emergencies  and  the 
care  of  drills. 

i.  The  repeated  sticking  of  a  bit  in  a  hole  is  most  exas- 
perating to  the  drill  runner,  and  the  usual  remedy  is  to  strike 
the  drill  shank  viciously  with  a  sledge  until  the  bit  comes 
loose.  It  is  needless  to  add  that  this  remedy  often  kills  the 
patient,  like  other  heroic  treatments.  A  moderate  blow  on 
the  drill  shank,  near  the  hole,  is  a  reasonable  and  often  suc- 
cessful means  of  loosening  a  stuck  bit.  A  blow  should  never 
be  hard,  and  never  so  high  up  as  to  strike  the  chuck,  for  a 
bent  piston  or  a  broken  chuck  is  likely  to 'result  when  hard 
or  high  blows  are  struck. 


38          ROCK  EXCAVATION— METHODS  AND  COST. 

2.  When  a  bit  sticks,  nine  times  out  of  ten  the  cause  is  a 
crooked  hole ;  and  the  remedy  is  a  movement  of  the  machine 
bodily  to  counteract  the  tendency  of  the  hole  to  become 
crooked.    If  the  drill  sticks  repeatedly,  loosen  up  the  clamp 
that  the  shell  sets  in  and  determine  whether  the  drill  is  on 
line  with  the  hole.     If  it  is  not,  slacken  off  on  one  of  the 
tripod  legs  so  as  to  throw  the  drill  rod  against  the  side  of 
the  hole  in  the  direction  the  hole  is  crooking.    A  lazy  driller 
will  hammer  his  drill ;  a  good  driller  will  reline  it. 

3.  If  the  bit  strikes  an  inclined  layer  of  rock,  and  particu- 
larly if  that  layer  is  harder  than  the  rock  above,  the  bit  will 
glance  off  toward  the  "down  hill"  side  and  probably  stick. 
The  best  remedy  that  I  have  found  in  this  case  is  to  drop  a 
number  of  fragments  of  gas  pipe,  or  other  chips  of  iron,  into 
the  hole.    These  fragments  of  iron  are  forced  into  the  soft 
rock  on  the  lower  side,  and  practically  produce  a  level  sur- 
face for  the  bit  to  strike  upon.     Old  ^4  in.,  or  larger,  gas 
pipe  should  be  cut  up  into  bits  with  a  cold-chisel  for  this 
purpose.    If  the  inclined  layer  of  hard  rock  is  not  very  hard, 
small  quartz  pebbles,  or  the  like,  will  serve  instead  of  iron. 

4.  In  any  case,  when  a  drill  sticks,  shorten  the  stroke  of 
the  drill  by  feeding  down  the  feed  screw,  so  that  the  air  or 
steam  may  get  between  the  piston  and  the  front  head ;  and 
work  for  a  time  with  short  strokes. 

5.  Often  the  cause  of  sticking  is  in  the  bit  itself,  which 
may  have  a  broken  ear,  or  the  drill  rod  or  shank  may  not 
be  exactly  central  with  the  center  of  the  bit,  due  to  poor 
blacksmith  work. 

6.  If  the  rock  produces  a  clay  sludge  that  adheres  to  the  bit 
and  causes  sticking,' a  pipe  may  be  put  down  in  the  hole  after 
removing  the  drill,  and  a  steam  or  air  jet  blown  through  it. 
This  will  effectually  clean  out  the  sludge  when  other  means 
fail.     Ordinarily,  however,  all  that  is  necessary  is  to  crank 
the  drill  back,  pour  in  a  cup  of  water,  turn  on  about  a  quar- 
ter of  the  head  of  air  and  churn  the  stiff  mud  as  the  machine 
is  cranked  up. 


MACHINE  DRILLS  AND  THEIR  USE.  39 

7.  The  softer  the  rock  the  more  rapidly  does  the  sludge 
accumulate.     To  remove  the  sludge  as  fast  as  it  forms,  a 
jet  of  water  is  most  effective.    A  small  pipe  is  kept  in  the 
hole  alongside  the  drill  rod,  and  water  is  continuously  forced 
through  the  pipe,  either  by  gravity  or  by  steam  or  air  pres- 
sure.    In  some  rocks  the  increased  number  of  feet  drilled 
per  day  after  a  water  jet  is  installed  is  astounding — amount- 
ing often  to  a  40  per  cent,  increase. 

8.  When  moving  the  drill  from  place  to  place  the  piston 
should  be  kept  inside  the  cylinder,  for  otherwise  it  may  be 
bent  if  the  drill  is  allowed  to  fall. 

9.  A  good  mineral  cylinder  oil  should  be  used  in  the  air 
chest,  and  from  there  it  passes  into  the  cylinder.     Feed  in 
a  small  amount  at  frequent  intervals,  and  on  a  new  drill  use 
an  excess  of  oil  for  the  first  few  days,  because  the  moving 
parts  of  a  new  machine  fit  tight  and  hold  very  little  oil  at 
one  time. 

10.  In  cold  weather,  when  steam  is  used,  the  stuffing  box 
should  be  unscrewed  to  let  the  water  out  of  the  cylinder  by 
inclining  the  drill  on  its  side  so  as  to  drain  the  steam  chest 
and  back  head. 

n.  When  the  machine  is  not  in  use  it  is  important  to 
keep  the  valve  and  piston  well  oiled,  otherwise  rust  will 
rapidly  eat  away  the  machined  surfaces. 

12.  Keep  on  hand  a  supply  of  U-bolts  and  nuts,  and  have 
the  blacksmith  learn  to  make  them,  as  their  life  is  short  at 
best.    A  bolt  that  permits  a  nut  to  work  loose  should  be  dis- 
carded at  once,  for  it  is  the  poorest  kind  of  economy  to  con- 
tinue using  it.    A  supply  of  pawls  and  pawl  springs  should 
also  be  kept  in  stock,  for  while  a  drill  will  work  with  one 
pawl    (after  removing  the  broken  one),  it  will  not  work 
economically.     Much  of  the  poor  work  done  by  drills  may 
be  attributed  to  working  with  one"  pawl. 

13.  In  hard  rock  it  often  happens  that  a  bit    dulls    so 
rapidly  that  its  ears  wear  off  more  than  is  usual ;  in  which 
case  the  hole  becomes  smaller  than  usual,  and,  as  a  conse- 


40          ROCK  EXCAVATION— METHODS  AND  COST. 

quence,  the  next  new  bit  will  stick  on  the  sides  of  the  hole 
before  reaching  the  bottom.  In  this  case  insert  the  shank 
into  the  chuck,  crank  up  close,  turn  on  the  air  without  tight- 
ening the  nuts  of  the  U-bolt  of  the  chuck.  This  will  drive 
the  bit  straight  to  the  bottom  of  the  hole.  Pull  it  up,  turn 
the  bit,  and  in  like  manner  drive  the  bit  down  in  a  new  posi- 
tion ;  repeat  this  operation  once  more  and  the  hole  will  prob 
ably  be  reamed  sufficiently  to  proceed  with  the  regular 
drilling. 

14.  When  a  drill  is  choked  in  the  hole  and  cannot  be  loos- 
ened by  hammering,  it  is  often  possible  to  loosen  it  by  run- 
ning with  a  loose  chuck  as  just  described,  and  turning  the 
drill  with  the  hands  during  the  back  stroke  of  the  piston. 

Use  of  the  Column  or  Bar. — In  the  early  days  of  tunneling 
machine  drills  were  mounted  on  cars  running  on  tracks,  and 
this  is  still  the  practice  in  Europe ;  but  in  America  the  drill 
is  usually  mounted  on  column  (Fig.  5)  or  bar  made  of  3 
to  5^2-in.  pipe  provided  with  one  or  two  screw  jacks  at  one 
end.  In  tunneling  the  column  is  usually  set  upright  with 
blocks  of  wood  between  its  ends  and  the  rock,  although  in 
narrow  headings  it  is  often  found  preferable  to  set  the  bar 
horizontally  just  as  is  done  of  necessity  in  shaft  sinking.  The 
machine  is  mounted  on  an  arm  projecting  from  the  column. 
The  advantage  of  the  column  method  over  the  car  method  of 
mounting  drills  is  that  without  waiting  for  the  blasted  rock 
to  be  entirely  cleaned  away,  the  drillers  can  set  up  and  get 
to  work.  A  column  is  preferable  to  a  tripod  where  it  can 
be  used,  for  it  gives  a  firmer  support  and  there  is  in  conse- 
quence less  liability  of  the  hole  running  crooked.  Moreovei 
in  a  stope  where  the  men  stand  on  loose  rock  it  is  very  diffi- 
cult to  get  a  solid  footing  for  each  of  the  three  tripod  Ieg3 
without  laying  a  substantial  flooring  of  some  kind  to  work 
upon. 

In  mining  work  it  is  advisable  to  have  an  assortment  of 
bars ;  for  one  driller  may  require  a  bar  3^  ft.  long  for  a 


MACHfNE  DRILLS  AND  THEIR   USE.  41 


Fig.  5- 


42          ROCK  EXCAVATION— METHODS  AND  COST. 

horizontal  set  up,  whereas  another  may  find  a  9  ft.  bar  none 
too  long  for  an  upright  set  up. 

1.  Blocks  of  tough  wood,  reasonably  free  from  knots,  are, 
placed  between  the  ends  of  the  bar  and  the  rock.     Sawed 
wedges  about  I  ft.  long  and  of  varying  thickness  at  the  butt 
are  preferable;  but  blocks  that  are  flat  on  the  side  next  to 
the  rock  and  rounded  on  the  side  next  to  the  bar  may   be 
used.    Most  of  the  blocking  should  be  placed  at  the  jacking 
end  of  the  bar  if  possible ;  a  2-in.  piece  properly  wedged  up 
will  serve  for  the  other  end,  which,  in  a  vertical  set  up,  is 
the  upper  end  of  the  bar. 

2.  The  shoe  or  shoes  should  fit  squarely  on  the  blocking; 
and  to  this  end  the  bar  may  be  deflected  if  necessary. 

3.  Having  placed  the  blocking,  the  jack  screws  are  jacked 
up  until  the  column  is  solid,  after  which  the  safety  clamp 
is  put  on  and  its  screws  set  up.    If  the  set  up  is  on  the  rubble 
filling  of  a  stope  jack  up  a  little  at  a  time,  as  the  rubble 
settles  under  the  vibration  of  drilling,  and  thus  avoid  split- 
ting the  blocking  by  trying  to  jack  up  all  at  once. 

4.  The  column  arm  is  next  put  on  the  column,  but  its  nuts 
are  left  a  trifle  loose,  so  that  the  arm  may  be  swung  about. 

5.  The  saddle  clamp  is  slipped  over  the  arm  and  bolted 
with  the  clamp  side  up ;  and  the  machine  is  set  in  the  saddle 
and  swung  into  line  for  drilling. 

6.  To  swing  the  machine  so  as  to  drill  another  hole,  the 
safety  clamp  is  not  released  until  the  drill  has  been  pointed 
in  the  direction  of  the  new  hole ;  then  it  is  released    and 
clamped  in  the  new  position. 

7.  To  dismount  the  machine,  remove  the  drill  steel,  re- 
lease the  safety  clamp  and  slacken  the  arm  bolts,  so  that  the 
machine  may  be  lowered  gently  by  the  driller  as  far  as  it  will 
go,  and  the  machine  removed  from  its  saddle. 

8.  In  starting  a  hole  on  a  face  of  hard,  slanting  rock  lower 
the  machine  a  little  on  the  bar  and  drill  a  few  inches,  then 
raise  the  machine  and  catch  the  edge  of  the  hole  thus  started. 

Use  of  Water  in  Drilling. — A    simple    and    very    effec- 


MACHINE  DRILLS  AND  THEIR   USE.  43 

live  method  of  increasing  the  number  of  feet  of  hole  drilled 
in  soft  rock  is  the  use  of  a  water  jet  to  wash  the  sludge  out 
of  the  hole  as  fast  as  it  forms.    Fig.  5  shows  a  drill  with  a 
small  water  pot,  pipe  and  hose  equipment  for  throwing  a 
jet  of  water  into  the  hole  during  the  drilling.     The  water 
pot  holds  eight  gallons  and  is  provided  with  an    air    pipe, 
through  which  compressed  air  enters  to  force  the  water  out 
through  the  nozzle.    This  air  pipe  is  attached  to  the  side  of 
the  drill  cock.     The  eight  gallons  will  last  an  hour  or  two, 
depending  upon  how  steadily  the  machine  is  running ;  and  a 
boy  can  keep  a  large  number  of  water  pots  supplied  with       , 
water.    The  nozzle  may  be  a  piece  of  ^-in.  gas  pipe  drawn  j?  f   ( 
down  to  a  fine  point  at  the  end,  and  it  should  be  pushed  into    ' 
the  hole  as  the  drill  advances.     In  running  an  adit  or  drift 
water  may  be  supplied  by  gravity  from  an  upper  level. 

Mr.  H.  P.  Stow,  of  California,  is  authority  for  the  fol- 
lowing data  (Mining  and  Scientific  Press)  showing  the  ef- 
fectiveness of  a  water  jet  in  drilling: 

"Three  rounds  were  drilled  by  the  same  miner,  using  a 
2*4-inch  drill,  drilling  the  same  number  of  hours,  size,  and 
as  near  as  possible  the  holes  were  of  the  same  kind.  Two 
of  the  rounds  were  drilled  without  taking  down  the  bar,  and 
the  third  was  put  in  alongside  of  the  other  two.  He  drilled 
one  round  without  water,  one  with  water,  bailing  from  a 
bucket,  the  usual  method ;  and  the  third  with  water  under 
pressure  in  a  hose.  Without  water  he  drilled  32  ft.,  using 
38  drills;  with  water  by  bailing,  41^4  ft.,  using  33  drills; 
and  with  water  from  the  hose,  52  ft.,  using  37  drills — that  is. 
a  gain  of  30  per  cent,  depth  of  holes,  and  50  per  cent,  gain 
of  feet  per  drill,  with  bailing  over  drilling  dry;  a  gain  of 
62^/2  per  cent,  of  depth  of  holes  and  66  2-3  per  cent,  gain 
of  feet  per  drill,  using  the  hose  over  drilling  dry ;  and  a  gain 
of  24^2  per  cent,  depth  of  holes,  and  n,per  cent,  of  feet  per 
drill  by  using  hose  over  bailing  water  from  a  bucket.  All  of 
which  shows  that  there  is  not  only  a  gain  of  ground  drilled, 
but  a  saving  of  drill  bits  used  by  using  water  under  pres- 


44          ROCK  EXCAVATION— METHODS  AND  COST. 

sure,  instead  of  bailing  it  from  a  bucket  or  not  using  it  at  all. 
Besides  the  actual  gain  in  drilling  the  'pressure-water'  is  a 
saving  in  getting  rid  of  the  gases  in  the  pile  of  dirt  and  the 
dust  formed  in  drilling,  resulting  materially  in  the  better 
health  of  the  men,  freedom  from  powder  headache  and  min 
ers'  consumption,  and  increased  rapidity  of  getting  into  the 
face  to  remove  the  dirt. 

"The  accompanying  illustration,  Fig.  5,  shows  a  portable 
outfit  arranged  by  the  Rix  Compressed  Air  &  Drill  Co.,  San 
Francisco,  Cal.  It  consists  of  a  galvanized  pot  with  a  bail, 
holding  eight  gallons  of  water,  and  which,  the  manufacturer 
says,  has  been  tested  to  150  Ibs.  per  sq.  in.  pressure.  This 
pot  has  openings  for  admitting  air  pressure  on  the  water, 
for  attaching  the  water  hose,  for  filling  and  for  releasing 
the  air  when  filling  is  required.  There  are  two  small  pieces 
of  hose,  one  for  admitting  the  air  and  one  for  the  squirter. 
The  air  hose  is  attached  to  the  side  of  the  drill  cock  and 
lightning  couplings  are  used. 

"The  superintendent  of  the  North  Star  mine  at  Grass  Val- 
ley, Cal.,  writes  the  manufacturers :  'For  clear  water,  we 
put  up  small  barrels  on  each  level,  or  in  the  most  convenient 
place  where  there  is  a  drip,  and  run  the  clear  water  into 
this  barrel,  which  is  also  protected  from  dust  or  dirt.  A 
faucet  is  placed  at  the  bottom.  A  boy  with  a  heavy  galvan- 
ized watering  pot,  filled  with  a  small  nozzle,  distributes  the 
water  to  the  tanks.  A  tank  of  water  lasts  for  some  time. 
It  depends  on  how  steadily  the  machine  is  running  and  how 
careful  the  man  is  about  shutting  off  the  water  when  not 
using  it.  It  will  last  at  least  an  hour  or  two  anyway,  and 
one  boy  can  keep  forty  tanks  supplied  under  reasonable  con- 
ditions of  water  supply.' ' 

Concrete  is  exceedingly  troublesome  material  in  which  to 
drill  deep  holes ;  but  water  under  pressure  has  been  used 
very  effectively  with  a  wide  flare  bit  which  permitted  a  small 
copper  water  pipe  to  be  inserted  nearly  to  the  bottom  of  the 
hole.  The  chips  and  dust  were  thus  carried  off  by  the  water 


MACHINE  DRILLS  AND   THEIR   USE.  45 

before  they  could  wedge  the  bit,  enabling  drilling  to  be  done 
for  25  cts.  a  ft.  at  a  profit  where  previously  it  had  been  done 
at  a  loss. 

Other  Types  of  Machine  Drills. — The  Leyner  drill  is  an 
American  drill  especially  adapted  for  use  in  rock  where  a 
water  jet  enables  a  bit  to  cut  faster.  The  Leyner  drill  has  a 
hollow  drill  rod  through  which  the  compressed  air  forces 
the  water  which  escapes  through  holes  near  the  bit.  A 
small  steel  water  tank  having  a  capacity  of  18  gals,  is  said 
to  hold  enough  water  for  a  shift's  drilling.  The  compressed 
«',ir  is  said  to  be  the  principal  agent  in  cleaning  the  hole,  the 
water  laying  the  dust  and  assisting  in  the  cleaning.  The 
drill  steel  is  not  fastened  to  the  drill  piston,  and  is  not 
churned  up  and  down  in  the  hole,  but  is  struck  by  the  piston, 
which  also  rotates  the  drill  bit  automatically.  This  drill, 
therefore,  acts  like  a  hand  hammer  drill,  whereas  the  com- 
mon type  of  drill  acts  like  a  hand  churn  drill. 

The  Randt  rotary  drill  (see  page  333)  is  a  European  drill 
which  is  driven  by  hydraulic  motors,  the  water  being  under 
great  pressure.  The  bit  is  held  against  the  rock  by  hydraulic 
pressure  and  is  rotated  slowly,  its  cutting  teeth  chipping  off 
the  rock.  For  tunnel  work  it  has  proved  effective,  but  it  is 
not  likely  to  be  used  for  open  cutting  because  of  the  neces- 
sity of  forcing  the  bit  against  the  rock,  which  would  involve 
loading  it  with  great  weights.  The  pneumatic  plug  drill 
(see  page  189)  is  simply  a  pneumatic  hammer  used  for  rivet- 
ing. It  may  or  may  not  have  a  device  for  automatically 
rotating  the  bit.  Being  a  small  machine,  it  is  efficient  only 
for  drilling  shallow  holes.  I  can  find  no  reliable  record  of  its 
use  for  holes  more  than  I  ft.  deep.  For  drilling  plug  and 
feather  holes,  and  for  block  holing  boulders  and  large  rocks, 
this  type  of  drill  is  destined  to  have  an  ever-increasing  use. 
It  has  already  been  introduced  into  several  mines  and  into 
a  large  number  of  dimension  stone  quarries.  Contractors 
will  eventuallv  use  it  for  block  holing  big  rocks  in  open  cut 
excavation. 


46          ROCK  EXCAVATION— METHODS  AND  COST. 

The  Shaw  Pneumatic  Tool  Co.,  of  Denver,  has  recently 
put  on  the  market  a  pneumatic  plug  drill  with  a  light  column 
upon  which  it  may  be  mounted.  The  drill  is  held  against 
the  rock  by  air  pressure,  thus  relieving  the  driller  of  the 
strain  and  jar  incident  to  holding  it  in  his  hand.  Another 
feature  of  the  Shaw  drill  is  a  small  hole  through  the  drill 
steel,  through  which  the  exhaust  air  passes  and  forces  the 
dust  from  the  hole,  a  spray  of  water  being  used  to  lay  the 
dust. 

Electric  drills  (see  page  93)  have  been  on  the  market  for 
a  good  many  years  without  making  much  headway  in  point 
of  numbers  in  use.  It  is  not  improbable,  however,  that  for 
certain  classes  of  drilling  they  will  eventually  find  a  wide 
field  of  usefulness.  I  reserve  for  future  editions  a  discus- 
sion of  their  features,  trusting  that  users  of  electric  drills 
will  be  kind  enough  to  send  me  data  of  actual  results  under 
given  conditions. 

The  Automatic  Gasoline  Rock  Drill  Co.,  of  San  Francisco, 
has  recently  introduced  a  drill  operated  by  gasoline.  The 
explosion  of  the  gasoline  in  the  cylinder  drives  the  piston. 
Provision  is  made  for  taking  care  of  the  exhaust  and  the 
heat  generated  by  the  gasoline  explosions.  The  chief  claim 
made  for  this  drill  is  that,  by  its  use,  steam  boilers  and  com- 
pressor plants  are  dispensed  with.  This  is  a  type  of  drill 
that  may  prove  very  economic. 


CHAPTER  IV. 
STEAM  AND  COMPRESSED  AIR  PLANTS. 

Upon  the  selection  of  a  power  plant  for  drilling,  the  profits 
of  rock  excavation  largely  depend.  Whether  to  use  com- 
pressed air  or  steam  for  open-cut  excavation  is  often  deter- 
mined purely  by  guess  work.  I  have  asked  several  engin- 
eers and  managers  of  air  compressing  plants  to  explain  why 
it  is  that  compressed  air  is  efficient  for  drilling  in  spite  of 
steam  engine  inefficiency,  and  invariably  the  answer  has 
been  to  the  effect  that  when  steam  is  used  direct  in  the  drills 
there  is  a  great  loss  of  energy  in  the  heat  that  is  constantly 
radiated  along  the  steam  pipe  line.  One  manager  said :  "It's 
like  trying  to  heat  the  wide,  wide  world  with  your  steam 
pipe  line  as  the  radiator."  This  sounds  plausible,  and  I 
doubt  not  is  believed  by  many  to  offer  a  full  explanation  of 
the  fact  that  steam  operated  drills  are  not  economic  in  the 
consumption  of  coal;  but  that  this  reason  is  very  far  from 
the  truth  we  shall  see  presently.  Indeed,  if  the  greatest  loss 
of  fuel  energy  came  from  heat  radiated  by  the  steam  pipe 
line,  the  loss  could  be  practically  stopped  by  the  very  simple 
expedient  of  surrounding  the  pipes  with  a  lagging  of  as- 
bestos, hairfelt  or  the  like.  The  great  loss  comes  from  a 
different  source  entirely,  as  will  be  made  clear. 

Heat  Energy  and  Horse  Power. — The  work  required  to 
raise  I  Ib.  to  a  height  of  33,000  ft.,  or  to  raise  33,000  Ibs.  to 
a  height  of  I  ft.  is  33,000  ft.  Ibs.  (foot-pounds),  and  if  this 
work  is  done  in  I  minute,  it  is  I  horse  power  (i  H.  P.)  It 
has  been  found  by  experiment  that  if  778  ft.  Ibs.  of  work 
be  expended  in  churning  up  I  Ib.  of  water,  the  temperature 
of  the  water  will  be  raised  i°  F.  (F.  signifies  that  the 
common  Fahrenheit  thermometer  is  used  in  measur- 

47 


48          ROCK  EXCAVATION— METHODS  AND  COST. 

ing    the    temperature).    Hence   I   Ib.  cleg.*  =    778  ft.  Ibs. 

Since  I  H.  P.  —  33,000  ft.  Ibs.,  and  since  778  ft.  Ibs  =  i 
Ib.  deg.,  we  see  that  I  H.  P.  =  33,000  ft.  Ibs.  -f-  778  ft.  Ibs. 
=  42.42  Ib.  deg.  per  min.  In  a  word,  if  42.42  Ibs.  of  water 
are  heated  I  degree  per  minute,  the  heat  energy  is  exactly 
equivalent  to  I  horse  power. 

By  reference  to  "steam  tables"  in  any  mechanical  en- 
gineer's hand  book  it  is  found  that  to  make  I  Ib.  of  steam 
at  70  Ibs.  per  sq.  in.  gage  pressure  requires  1,146  Ib.  deg. 
of  heat  energy,  if  the  water  from  which  the  steam  is  made 
is  at  a  temperature  of  60°  F.  to  begin  with.  Now  we  have 
seen  that  42.42  Ib.  deg.  per  min.  =  i  H.  P. ;  therefore  since 
there  are  60  mins.  in  an  hour  60  X  42.42  =  2,545.2  Ib.  deg. 
are  equivalent  to  I  horse  power  per  hour.  Dividing  2,542.2 
Ib.  deg.  by  1,146  Ib.  deg.,  we  have  2.22  Ibs.  of  steam  (at 
70  Ibs.  gage  pressure  from  water  at  60°  )  as  the  equivalent  of 
i  H.  P.  That  is  if  one  horse  power  were  exerted  for  an 
hour  in  churning  up  water,  the  heat  developed  would  be 
equivalent  to  making  2.22  Ibs.  of  steam.  Reversing  the  op- 
eration, if  there  were  absolutely  no  losses  of  any  kind,  by 
radiation  or  otherwise,  in  the  engine,  2.22  Ibs.  of  steam  per 
hour  would  develop  i  H.  P. ;  but  in  practice  there  are  many 
unavoidable  losses  in  the  best  of  steam  engines.  The  ex- 
haust steam  itself  carries  away  a  tremendous  amount  of 
energy  that  is  lost.  The  following  table  shows  in  a  striking 
manner  how  inefficient  the  steam  engine  is  at  best: 

Lbs.  of  Steam 


Kind  of  Engine. 
Theoretically   Perfect    (steam  at  70 
Ibs.  gage  from  water  at  60°)  .  .  . 
Compound    (good)     

per  I.  H.  P.f 
per  hr. 

2.22 

15  to  20 

Steam 
Efficiency. 

1  00% 
14.8%  to  11.1% 

Single    Condensing      

23 

0  7% 

Large    Non-condensing    (good)  .... 
Average    Size    Condensing  
Small    Non-condensing     

28 
30 
30  to  6s? 

8% 

7-4% 
7.4%  to  3.4% 

*  The  expression  "pound  degree"  abbreviated  to  "Ib.  deg."  will  be  used  in- 
stead of  the  common  but  cumbersome  expression,  "British  thermal  unit"  (B.  T. 
U.).  When  2  Ibs.  of  water  are  heated  so  as  to  raise  its  temperature  30  degrees, 
the  heat  energy  imparted  to  the  water  is  2  X  30  =  60  Ib.  degs.,  which  is  more  in 
keeping  with  our  system  of  indicating  work  in  foot-pounds  than  to  say  60 
B.  T.  U. 

f  I.   H.    P.   is   "indicated  horse  power"  as  measured   with  a   steam    indicator; 


STEAM  AND  COMPRESSED  AIR  PLANTS.  49 

When  we  stop  to  consider  what  these  figures  mean,  we 
wonder  how  an  air  compressor  run  by  a  steam  engine  can 
possibly  compete  with  steam  used  direct  in  the  drill;  for  if 
the  heat  efficiency  of  the  engine  that  drives  the  compressor 
is  only  n  per  cent.,  it  means  that  out  of  every  100  Ibs.  of 
steam  only  n  Ibs.  are  utilized  to  their  fullest  value,  and  that 
89  Ibs.  virtually  escape  into  the  air  without  doing  any  useful 
work.  But  even  this  low  efficiency  does  not  mark  the  end 
of  the  losses  in  an  air-compressing  plant,  for  the  act  of  com- 
pressing the  air  raises  its  temperature,  and  if  the  temper- 
ature is  not  kept  constant  during  the  process  of  compres- 
sion a  certain  amount  of  useless  work  is  done  by  the  com- 
pressor engine. 

The  Work  of  Compression. — If,  by  means  of  circulating 
water,  it  were  possible  to  prevent  the  temperature  of  air 
from  rising  during  the  process  of  compression,  the  efficiency 
of  compression  would  be  100  per  cent. ;  but  if  the  temper- 
ature is  permitted  to  rise  the  air  is  expanded  accordingly 
and  exerts  a  back  pressure  upon  the  engine.  Then  as  the 
compressed  air  quickly  loses  this  high  temperature  in  the  re- 
ceiver and  in  the  pipe  line,  it  loses  some  of  its  pressure, 
which  represents  just  so  much  wasted  energy. 

It  is  customary  to  rate  air  compressors  by  the  number  of 
cubic  feet  of  "free  air"  that  the  compressor  will  compress 
to  a  given  gage  pressure  per  minute.  By  "free  air"  is  meant 
the  ordinary  air  at  sea  level  and  at  a  temperature  of  60°  F. 
The  volume  of  the  compressed  air  as  compared  with  free 
air  is  given  in  the  fourth  column  of  Table  IV. 

The  standard  practice  for  large  plants  now  is  to  compress 
the  air  in  a  low-pressure  compressor,  pass  the  air  through  an 
"inter-cooler,"  and  then  finish  the  compression  to,  say,  75 
Ibs.,  in  a  high-pressure  compressor.  This  raises  the  effi- 
ciency of  compression  to  about  84  per  cent. 

B.  H.  P.  is  "brake  horse  power"  as  measured  with  a  Prony  brake.  The  B.  H.  P. 
of  an  engine  is  from  10  to  20  per  cent,  less  than  the  I.  H.  P.,  due  to  the  fric- 
tion losses  in  the  engine. 


50          ROCK  EXCAVATION— METHODS  AND  COST. 

Table  IV.  gives  the  number  of  horse  power  required  to 
compress  air  under  the  most  favorable  and  under  the  worst 
possible  conditions. 

TABLE  IV. 

BRAKE   (OR  DELIVERED)   HORSE-POWER  REQUIRED  TO  COMPRESS  ONE 

CUBIC  FOOT  OF  FREE  AIR  PER  MINUTE  TO  A  GIVEN  GAGE 

PRESSURE.     (HASWELL.) 

HI        lli 


50                  .1195                  .0951  .2272 

55                     -1270                     .0994  .2109 

60                     .1342                     .1040  .1968 

65                  .1403                  .1081  .1844 

70                .1472                .1124  .1735 

75                    -1537                    -1163  -1639 

80                    .1597                    -1193  -1552 

85                    .1655                    .1224  .1474 

90                    .1710                    .1256  .1404 

95                     -1763                     -1289  .1340 

100                     .1815                     .1312  .1281 

For  the  purpose  of  comparing  compressed  air  with  steam 

Table  V.  will  be  found  useful : 

TABLE  V. 

STEAM  VOLUME  AND  TEMPERATURE  AT  GIVEN  PRESSURES. 
Gage  Pressure,     Temperature,      Lb.  Degs.  from  Cu.  ft.  occupied  by 

Lbs.  per  sq.  in.      Fahrenheit.           Water  at  32°.  i  Ib.  of  Steam. 

50.3                     297.8                     1,172.8  6.53 

55-3                     302.7                      1,174-3  6.09 

60.3                     3074                     1,175-7  5-71      . 

65.3                     3H.8                      i,i77.o  5-37 

70.3                     316.0                     1,178.3  5.07 

75-3                     320.0                     1,179-6  4-8 1 

80.3                     323.9                     1,180.7  4-57 

85.3                     327.6                     1,181.8  4-36 

90.3                     331.1                      1,182.9  4.16 

95-3                     334-5                      1,184.0  3-98 

100.3                     337-8                     1,185.0  3-82 
Before  we  discuss  the  relative  efficiency  of  air  and  steam 
it  will  be  best  to  consider  the  amount  of  power  required  to 
operate  a  drill. 

*  Adiabatic. 
t  Isothermal. 


STEAM  AND   COMPRESSED  AIR  PLANTS.  51 

Tests  of  Air  Consumed  by  Drills. — There  are  very  few  re- 
liable tests  on  record  showing  the  actual  air  consumption  of 
drills,  yet  data  of  some  kind  must  be  used  by  every  engineer 
who  has  to  determine  the  size  of  compressor  plant  needed  to 
operate  a  given  number  of  drills.  The  data  given  in  cata- 
logues will  not  satisfy  many  engineers.  I  have,  therefore, 
given  considerable  space  to  such  records  of  actual  tests  as 
I  could  find,  and  to  the  discussion  of  the  tests  compared  with 
catalogue  data.  By  all  odds  the  most  satisfactory  records 
of  actual  air  consumption  of  drills  are  to  be  found  in  a  paper 
by  Messrs.  J.  B.  Carper,  E.  Goffe  and  W.  C.  Docharty,  re- 
cently read  before  the  Mechanical  Engineers'  Association 
of  the  Witwatersrand.  Some  very  interesting  data  are 
given  of  the  air  consumption  of  a  number  of  English  and 
American  rock  drills.  The  authors  state  that  they  endeav- 
ored to  conduct  a  fair  and  unbiased  trial  of  all  the  rock  drills 
procurable,  which  represent  nearly  all  of  those  on  the  Jo- 
hannesburg market.  The  object  of  the  trials  was  to  obtain 
the  quantity  of  air  consumed  by  the  different  makes  and 
sizes  of  drills  while  doing  the  same  work. 

The  method  of  making  the  tests  was  as  follows :  All  the 
holes  were  drilled  in  a  block  of  red  granite,  2  ft.  thick,  hav- 
ing the  same  density  and  hardness  as  that  of  Peterhead 
granite.  The  block  was  bedded  in  concrete,  and  the  drills 
were  mounted  on  a  quarry  bar  supported  by  A  frames  firmly 
set  in  concrete.  All  holes  were  drilled  vertically.  There 
were  two  air  receivers,  5  X  20  ft.  each,  having  a  combined 
capacity  of  757  cu.  ft.  The  air  compressor  was  worked  until 
the  gage  on  the  receivers  showed  a  pressure  of  80  Ibs.  per 
sq.  in. ;  then  the  stop  valve  was  shut,  closing  connection  with 
the  receiver.  Drilling  was  then  begun  with  the  machine  to 
be  tested,  and  continued  without  intermission  until  the  gage 
registered  70  Ibs.  The  machine  was  then  stopped,  and  the 
depth  and  diameter  of  the  hole  carefully  measured.  A 
similar  run  was  made  from  70  to  60  Ibs.,  and  so  on  down 
to  35  Ibs.  pressure.  In  working  out  the  results  the  capacity 


52          ROCK  EXCAVATION— METHODS  AND  COST. 

of  the  receivers  was  calculated  for  every  pressure  (80  down 
to  35  Ibs.),  corrected  for  temperature,  and  the  air  consump- 
tion reduced  to  the  equivalent  of  free  air  at  70°  F.  and  24.8 
ins.  barometer. 

The  first  set  of  tests  was  upon  14  drills  having  3*4-in. 
cylinders  and  using  3-in.  bits.  Space  will  not  permit  re- 
printing the  tabulated  results  of  all  these  tests  but  I  have 
calculated  the  average  results  of  the  tests  on  13  of  the  drills, 
eliminating  one  drill  which  behaved  in  a  very  erratic  man- 
ner, and  likewise  eliminating  a  few  individual  runs  which 
showed  great  departure  from  other  performances  of  the 
same  make  of  drill.  The  following  table  gives  the  average 
results  of  13  drills  having  334~m-  cylinders  and  using  3-in. 
bits: 

TABLE  VI. 

Air  pressure,  Ibs 80-70   70-60    60-50   50-40    40-35 

Cu.  ft.  free  air  per  min 124       117       100         70         60 

Cu.  ft.  free  air  per  lin.  in.  of  hole..  95.3  106.4  100.0  116.4  120.0 
Cu.  ft.  free  air  per  cu.  in.  of  hole. .  13.3  14.8  13.8  15.0  16.6 
Lin.  ins.  drilled  per  min 1.3  i.i  i.o  '  0.6  0.5 

In  studying  this  table  we  see  that  the  air  consumption  per 
inch  drilled  is  somewhat  erratic,  but  it  was  much  more  er- 
ratic in  individual  tests.  The  reason  for  this  may  be 
ascribed  in  part  to  the  lack  of  uniformity  in  the  granite,  in 
the  personal  equation  of  the  driller  and  in  the  efficiency  of 
the  drill  itself  at  different  air  pressures.  Doubtless  the  tem- 
pering and  sharpening  of  the  bits  had  a  marked  effect  also. 
Each  drill,  it  should  be  stated,  was  run  by  men  selected  by 
the  agent  of  the  drill,  so  that  the  personal  equation  becomes 
a  factor  of  importance.  However,  the  personal  equation  of 
the  driller  is  by  no  means  of  so  great  importance  on  short 
continuous  runs  like  these  as  upon  runs  several  hours  long. 
In  the  trials  each  run  was  about  6  mins.  long ;  that  is,  a  run 
of  the  drill  during  the  drop  of  10  Ibs.  in  air  pressure  con- 
sumed on  the  average  about  6  mins. 

One  thing,  however,  is  strikingly  and  consistently  shown 
in  the  above  tabulation,  namely,  the  rapid  falling  off  of 


STEAM  AND   COMPRESSED  AIR  PLANTS. 


53 


inches  penetrated  per  minute  with  every  drop  in  the  air 
pressure.  With  air  pressure  averaging  75  Ibs.  we  note  that 
1.3  ins.  per  min.  were  drilled,  as  against  only  0.6  ins.  per 
min.  under  an  average  pressure  of  45  Ibs.  The  lesson  that 
this  teaches  is  that  it  does  not  ordinarily  pay  to  overload 
an  air  compressor  with  more  drills  than  it  is  designed  to 
carry,  and  that  it  never  pays  to  use  a  main  pipe  so  small 
as  to  reduce  the  air  pressure  materially. 

It  is  interesting  to  note  that  American  drills  were  well  in 
the  lead  of  competitors.    The  best  record  of  all  the  3^4-in. 
machines  was  made  by  a  Rand  "Slugger."   Using  a  3-in.  bit 
this  drill  showed  the  following  results : 
TABLE  VII. 

Air  pressure,   Ibs 80-70      70-60     60-50 

7,583 


50-40     40-35        80-35 
8.550    11.666      6.416    41.381 


Length  of  run,  mins.  .     7.166 
Cu.  ft.  of  free  air  per 

min 91.1         84.9        76.4        52.8        46.1        69.2 

Cu.  ft.  of  free  air  per 

lin.  in.  of  hole... .  61.5        76.9        78.0        96.7      105.3        78-3 
Cu.  ft.  of  free  air  per 

cu.  in.  of  hole.  ...  8.70  10.80  11.04  13.68  14.90  11.08 
Linear  inches  per  min.  1.48  i.io  0.98  0.54  0.44  O.88 
The  excellence  of  the  performance  of  this  drill  is  well 
shown  by  comparing  the  results  of  its  test  with  those  above 
given  as  the  average  of  13  drills  of  the  same  size.  Mr. 
Docharty  attributes  the  poor  showing  made  by  most  of  the 
drills  to  poor  valve  design  resulting  in  cushioned  blows ; 
and  he  suggests  that  perhaps  a  study  of  these  tests  will  lead 
some  of  the  manufacturers  to  improve  their  valve  designs. 
There  were  only  four  3-in.  machines  tested,  and,  while  in 
some  instances  the  results  were  erratic,  the  air  consumption 
and  speed  of  drilling  (3-in.  bits)  correspond  very  closely 
with  the  data  above  given  for  the  13  larger  drills.  It  should 
be  remembered,  however,  that  no  tests  were  made  in  deep 
holes,  for  under  those  conditions  the  larger  machines  would 
doubtless  show  their  superiority.  The  fact  that  only  shallow 
vertical  holes  were  drilled  should  not  be  lost  sight  of  in  con- 
sidering these  tests. 


54          ROCK  EXCAVATION— METHODS  AND  COST, 

One  of  the  most  valuable  of  the  tests  made  was  one  with 
a  2^4-in.  Rand  "Slugger,"  using  bits  of  different  size,  li 
has  been  claimed  that  the  depth  of  hole  drilled  in  a  given 
time  should  vary  inversely  as  the  area  of  the  hole,  but  there 
is  little  in  the  way  of  actual  tests  to  substantiate  this  claim. 
While  too  much  reliance  should  not  be  placed  upon  one  or 
two  tests,  the  following  data  tend  to  prove  that  in  drilling 
granite  the  speed  of  drilling  varies  inversely  as  the  square  of 
the  diameter  of  the  bit.  A  2%-in.  "Slugger"  with  a  6I/4~ir\. 
stroke  gave  the  following  results : 

TABLE  VIII. 

Air  pressure  Ibs 80-71  71-67  60-52     50-44  80-44 

Diam.  of  bit,  ins 2Yi8        2  2%       2%  2  to  2^ 

Length  of  run,  mins 8.08      1.08  9.25      6.83  25.25 

Ins.  drilled  per  min 2.19      3.81  1.81      0.95  1.78 

Cu.  ft.  free  air  per  min...  72.5  224.2  50.2  47.3  64.0 

"      "       "      "       "     Hn.    in.  33.0  58.8  27.7  49.7  35.8 

"    cu.   in..  9.88  18.72  7.83  14.03  10.45 

Air  pressure,   Ibs 80-70  70-60  60-50  50-40  40-37  80-37 

Diam.   of   bit,    ins,...  3Vie  3Yie  333          3  to  3Y*» 

Length  of  run,  mins..  8.75  8.0  10.25  13-6?  5«o8  45.75 

Ins.   drilled  per  min..  1.08  0.64  0.69      0.56  0.51          0.70 
Cu.    ft.    free    air    per 

min 69.7  72.0  56.8  43.8  33.2  55.4 

Cu.    ft.    free    air    per 

lin.   in 64.2  112.4  81.7  77.3  64.3  78.9 

Cu.    ft.    free   air   per 

cu.  in 8.75  15.26  11.56  10.93  9.11  11.09 

It  will  be  seen  that  with  a  bit  of  2  1/16  ins.  in  diam.,  the 
average  speed  was  1.78  lin.  ins.  of  hole  per  min.;  but  with 
a  bit  of  3  1/32  ins.  in  diam.,  the  average  speed  was  only  0.70 
lin.  ins.  per  min.  A  similar  series  of  tests  with  a  Climax 
machine  of  the  same  size  gave  an  average  of  i.i  lin.  ins. 
of  hole  per  min.  with  a  3-in.  bit,  as  against  1.85  lin.  ins.  with 
a  2-in.  bit.  So  far  as  I  know  these  are  the  only  published 
tests  of  drilling  done  under  precisely  the  same  conditions 
with  bits  of  different  diameters,  and  it  is  much  to  be  desired 
that  further  tests  be  made  on  different  kinds  of  rock  to 


STEAM  AND  COMPRESSED  AIR  PLANTS.  55 

establish  the  ratio  of  speeds  using  different  sized  bits  in  the 
same  drill. 

In  a  rock  that  makes  sludge  rapidly  as  for  example 
shales,  slates,  and  some  porphyries,  a  drill  using  water 
under  pressure  for  washing  out  the  sludge  will  readily  ex- 
cel drills  which  depend  upon  the  "chuck-tending"  of  the 
drill  helper.  As  illustrating  this  point  Table  IX  shows  that 
the  Leyner- Water  drill  showed  up  very  poorly  in  compari- 
son with  other  drills  in  these  tests  for  air  economy ;  yet  this 
same  Leyner- Water  drill  has  made  some  remarkable  records 
(page  78)  in  competition  with  other  drills  working  in  softer 
rocks  which  make  sludge  rapidly.  Apparently  the  agents 
of  the  drills  themselves  did  not  in  every  case  appreciate  the 
difference  in  results  that  occur  in  drilling  different  kinds 
of  rock,  nor  do  the  authors  of  this  valuable  paper  mention 
this  factor  as  being  one  of  importance  in  comparing  drill 
efficiencies. 

TABLE  IX. 

TEST  OF  LEYNER- WATER  DRILL. 
(Bore,  3  ins.;  stroke,  3  ins.;  weight,   156  Ibs.) 

Air  pressure,  Ibs 80-70        70-60  80-70        70-60        80-60 

Diam.  of  bit,  ins 2*/u         2L/lt  2l/s           2%     21/i6-2l/» 

Length  of  run,  mins..       5V3           6Ye  7              6*/2            25 

Ins.   drilled  per  min..  .       1.50          1.37  1.21           1.25             1.32 
Cu.     ft.     free    air    per 

mini.    115.2        100.8  86.9          93.8            98.2 

Cu.     ft.     free    air    per 

Hn.   in 76.8          73.1  71.6          75.0             74.1 

Cu.     ft.     free    air    per 

cu.   in 23.0          21.89  20.2          21. 16           21.52 

Test  of  Air  Consumption  at  the  Rose  Deep  Mine. — A  6-hr, 
run  at  the  Rose  Deep  Mine,  South  Africa,  showed  the  fol- 
lowing results  for  31  drills:  The  compressed  air  averaged 
70  Ibs.  per  sq.  in.  and  each  3^-in.  drill  consumed  81  cu.  ft. 
of  free  air  per  minute,  including  all  leakage  of  pipes  (there 
was  less  leakage  than  is  common  in  mines).  Each  drill  re- 
quired 43  Ibs.  of  coal  per  hour,  to  supply  this  compressed 
air;  and  each  pound  of  coal  developed  3.4  H.  P.,  per  hour, 


56          ROCK  EXCAVATION— METHODS  AND  COST. 

by  the  indicator  on  the  steam  engine,  evaporating  6.74  Ibs. 
of  water  from  212°  F.  The  average  horse-power  of  the 
compressor  engine  was  12.7  I.  H.  P.  per  drill;  but  all  the 
drillers  were  trying  to  make  a  record  and  accomplished  in 
6  hrs.  an  amount  of  drilling  that  ordinarily  took  8  hrs.  It 
was  an  efficient  steam  power  plant,  as  is  seen  by  the  fact 
that  3.4  H.  P.  were  developed  with  each  pound  of  coal. 
The  power  plant  was  a  vertical  King-Reidler  Compound 
Steam'  Engine  and  Double  Stage  Air  Compressor  with  two 
boilers  of  the  horizontal  return  tubular  type.  The  engine 
developed  393  I.  H.  P.  and  had  a  mechanical  efficiency  of 
86  per  cent.  There  were  several  sizes  of  machine-drills 
used,  but  they  were  all  reduced  to  the  3^4-in.  size  as  standard 
by  the  test  of  filling  the  cylinders,  ports,  etc.,  with  water  and 
ascertaining  the  volume  of  water  for  each  drill  cylinder. 
This  showed  the  rating  of  the  drills  in  air  consumption  to 
be  as  follows: 

Relative  Air 
Consumption 

2l/2-\n.  drill ' 0.445 

3%-in ' i.ooo 

3  5-T6-in 1.069 

32lHn 1.123 

The  31  drills  averaged  4.5  ft.  of  hole  drilled  per  hour  for 
the  6-hr,  run;  one  3>^-in  drill  making  52  ft.  of  hole  in  6 
hrs.,  drilling  4  dry  holes.  Comparing  the  consumption  of 
81  cu.  ft.  of  free  air  per  min.,  at  70  Ibs.,  with  the  average 
of  1 20  cu.  ft.  (at  70  Ibs.)  given  in  Table  VI,  gives  a  fair 
idea  of  the  difference  between  a  long  test  using  a  number  of 
drills,  and  a  short  test  of  one  drill. 

For  purpose  of  comparison  I  would  add  that  a  recent  gov- 
ernment report  states  that  2,300  air  drills  are  in  use  in  South 
Africa,  70  per  cent,  of  which  are  3^-in.  drills,  and  each 
drill  requires  12  I.  H.  P.  of  steam  engine  to  run  the  two- 
stage  air  compressors  that  supply  the  air. 

Tables  of  Air  Consumption  in  Catalogues. — Table  X  is 
given  in  the  catalogue  of  one  of  the  well-known  drill  manu- 
facturers, and  is  said  to  be  based  upon  actual  tests  of  single 


STEAM  AND  COMPRESSED  AIR  PLANTS.  57 

drills  running  continuously  without  stops  for  changing  bits, 
etc. 

TABLE  X. 

CUBIC  FEET  OF  FREE  AIR  PER  MINUTE  REQUIRED  TO  RUN  A  ONE- 
DRILL  PLANT. 


B 

<u  3 

6? 

70 
80 
90 

IOO 

Diameter 

of  Drill  Cylinder. 

2" 

SO 
56 
63 
70 

77 

60 

68 
76 
84 
92 

68 

77 
86 

95 
104 

23/4' 
82 

93 
104 

"5 

126 

'  3" 
90 

IO2 
114 
126 
138 

3%" 
95 
108 
1  20 

133 
146 

33Ae" 
97 
no 

123 

136 

149 

ZY4"  3/2"  3tt" 
100  108  113 
113  124  129 
127  131  143 
141  152  159 
154  166  174 

43/4" 

130 
147 
164 
1  182 
199 

5" 
ISO 
170 
190 

2IO 
240 

5/2" 
I64 

181 
207 
230 
252 

When  more  than  one  drill  is  to  be  supplied  from  the 
same  air  compressor  the  manufacturers  advise  multiplying 
the  quantities  given  in  Table  X  by  the  factors  given  in  Table 
XL 

TABLE  XL 

Number  of  drills 12       5       10       15       20       30       40       70 

Multiply      value      in 

Table  X    by I     1.8    4.1      7.1      9.5     11.7     15.8    21.4    33.2 

Tables  similar  to  these  are  given  by  other  manu- 
facturers. In  answer  to  letters  of  inquiry  I  have  been 
informed  that  such  tables  are  "based  upon  experience  in  a 
large  number  of  mines."  In  view  of  the  actual  tests  above 
given,  tables  in  catalogues  should  be  used  with  caution. 
Certainly  the  "experience"  in  all  mines  is  not  the  same,  and, 
if  it  were,  it  would  differ  widely  from  "experience"  in  open 
cut  work  where  drills  usually  work  more  continuously. 

In  the  next  chapter  it  will  be  shown  that  the  actual  drill- 
ing time,  that  is,  the  time  when  the  drill  is  actually  striking 
blows,  is  seldom  over  70  per  cent,  and  often  not  more  than 
40  per  cent,  of  the  length  of  the  shift.  Knowing  the  condi- 
tions of  work,  the  reader  will  be  able  (with  the  aid  of  data 
given  in  the  next  chapter)  to  predict  approximately  the  per 
cent,  of  actual  drilling  time.  Then  if  there  are  more  than, 
say,  10  drills,  he  can  multiply  the  air  consumption  of  one 
drill  (when  actually  drilling)  by  the  percentage  of  drilling 


58          ROCK  EXCAVATION— METHODS  AND  COST. 

time  in  the  shift,  and  the  product  will  be  the  average  air 
consumption  of  each  drill.  If  there  are  less  than  about  10 
drills  it  will  not  be  safe  to  figure  so  closely,  because  the 
fewer  the  drills  operated  from  one  compressor,  the  more 
likely  it  is  that,  all  or  nearly  all,  of  them  will  be  using  air 
at  the  same  time.  The  larger  the  number  of  drills,  on  the 
other  hand,  the  more  certain  it  is  that  some  will  be  changing 
bits  while  others  are  drilling,  and  thus  draw  a  steady,  aver- 
age amount  of  air  from  the  compressor. 

Steam  Consumption  in  Terms  of  Air  Consumption. — When 
steam-  is  piped  directly  from  the  boiler  into  a  drill,  practi- 
cally the  same  number  of  cubic  feet  of  steam  are  consumed 
as  of  cubic  feet  of  compressed  air.*  Referring  to  Table 
V  we  find  that  I  Ib.  of  steam  at  75  Ibs.  gage  pressure  occupies 
4.8  cu.  ft.,  or  i  cu.  ft.  steam  weighs  0.21  Ib.  Referring  to 
Table  IV.  we  find  that  I  cu.  ft.  of  free  air  is  equivalent  to 
0.1639  cu.  ft.  of  compressed  air  at  75  Ibs.  pressure,  or  i  cu. 
ft.  of  compressed  air  (at  75  Ibs.)  is  practically  equal  to  6  cu. 
ft.  of  free  air.  We  may  assume  that  a  cubic  foot  of  steam 
will  do  practically  the  same  work  in  a  drill  as  a  cubic  foot 
of  compressed  air  at  the  same  pressure,  because  neither  the 
steam  nor  the  air  acts  to  any  great  extent  expansively  in  a 
drill  cylinder,  due  to  the  late  cut-off.  This  being  so,  0.21  Ib. 
of  steam  is  equivalent  to  6  cu.  ft.  of  free  air,  or  i  Ib.  of  steam 
is  equivalent  to  nearly  30  cu.  ft.  of  free  air,  or  i  cu.  ft.  of 
free  air  is  equivalent  to  0.035  Ibs.  steam — all  at  the  same 
pressure  of  75  Ibs.  per  sq.  in.  If  a  drill  consumes  at  the  rate 
of  100  cu.  ft.  of  free  air  per  min.,  it  will  consume  6,000  cu. 
ft.  of  free  air  in  an  hour.  If  it  were  using  steam  in  its  cyl- 
inder instead  of  air  (at  75  Ibs.  pressure),  it  would,  there- 
fore, consume  6,000  X  0-035  =  210  Ibs.  of  steam  (at  75  Ibs. 
pressure)  in  an  hour.  Referring  to  Table  V.,  we  see  that  i 


*  The  chief  engineer  of  the  Rand  Drill  Co.  informs  me  that  he  estimates  10 
per  cent,  less  volume  of  steam  than  of  compressed  air  due  to  the  fact  that  steam 
passes  with  less  velocity  through  the  ports. 


STEAM  AND  COMPRESSED  AIR  PLANTS.  59 

Ib.  of  steam  (75  Ibs.  pressure),  made  from  water  at  32°,  con- 
tains 1,179  Ib.  clegs,  of  heat;  but,  as  the  feed  water  is  ordi- 
narily hotter  than  32°,  we  may  say  that  I  Ib.  of  steam  con- 
tains 1,150  Ib.  degs.  of  heat  energy  imparted  to  it  by  the  coal. 
Therefore,  if  a  steam  drill  were  to  consume  210  Ibs.  of  steam 
in  an  hour  it  would  use  210  X  1,150  =  241,500  Ib.  degs.  of 
heat  energy. 

From  Table  IV.  we  find  that  to  compress  I  cu.  ft.  of  free 
air  per  min.  to  75  Ibs.  pressure  requires  0.1163  H.  P.;  but 
we  have  seen  that  i  H.  P.  =  42.42  Ib.  degs. ;  hence  0.1163  X 
42.42  =  4.933  Ib.  degs.  per  min.  are  required  to  compress  I 
cu.  ft.  of  free  air  to  75  Ibs.  gage  pressure.  If  the  air  drill 
consumes  100  cu.  ft.  of  free  air  per  min.,  we  have  100  X 
4-933  =  493-3  Ib.  degs.  per  min.,  or  493.3  X  60  =  29,598 
Ib.  degs.  per  hour.  Now  comparing  these  29,598  Ib.  degs. 
in  the  hour's  work  of  the  drill  using  air,  with  the  241,500  Ib. 
degs.  in  the  hour's  work  of  the  same  drill  using  steam,  we 
see  the  true  reason  why  compressed  air  can  compete  with 
steam  in  spite  of  all  the  losses  of  power  involved  in  produc- 
ing the  compressed  air.  The  ratio  of  29,598  to  241,500  is 
practically  i  to  8.  In  other  words,  I  cubic  foot  of  steam,  at 
75  Ibs.  gage  pressure,  contains  eight  times  as  much  heat 
energy  as  one  cubic  foot  of  air  at  the  same  pressure,  yet  so 
far  as  running  the  drill  is  concerned  the  air  is  exactly  as 
valuable  as  the  steam.  If  window  weights  were  made  of 
gold  instead  of  cast  iron  they  would  not  be  one  whit  more 
effective  in  counterbalancing  the  weight  of  the  window,  so 
steam  is  not  more  effective  than  compressed  air  when  both 
act  directly  at  pressures  that  are  identical. 

Going  back  again  to  the  steam  engine  and  the  compressor 
it  should  not  be  forgotten  that  they  have  a  combined  effi- 
ciency of  not  much  more  than  10  per  cent. ;  hence  although  an 
air  drill  uses  only  29,598  Ib.  degs.  of  heat  energy  per  hour, 
it  required  10  X  29,598  =  295,980  Ib.  degs.  per  hr.  of  en- 
ergy in  the  form  of  steam  that  entered  the  compressor  en- 
gines to  produce  the  compressed  air  supplying  the  drill.  Com- 


60         ROCK  EXCAVATION— METHODS  AND  COST. 

paring  this  295,980  Ib.  degs.  of  energy  with  the  241,500  Ib. 
degs.  consumed  by  the  drill  using  steam  direct  we  see  that, 
if  there  is  no  loss  of  heat  energy  by  radiation  in  the  steam 
pipe  line,  it  takes  about  25  per  cent,  more  coal  to  run  each 
drill  when  compressed  air  is  used  than  when  steam  is  used 
in  the  drill.  Ordinarily,  however,  steam  pipes  are  left  bare, 
and  the  heat  radiated  is  nearly  sufficient  to  equalize  the  coal 
consumption. 

The  Efficiency  of  a  Steam  Pipe  Line. — When  steam  is  pass- 
ing through  a  wrought-iron  pipe  there  is  a  constant  loss  of 
heat  which  has  been  found  by  experiment  to  be  about  750 
Ib.  degs.  per  sq.  ft.  of  pipe  surface  per  hour,  when  the  sur- 
rounding air  is  still;  and  about  30  per  cent,  more  when  a 
wind  is  blowing.  This  is  upon  the  assumption  that  the  dif- 
ference of  temperature  between  the  steam  and  the  outside 
air  is  250°  F.  If  the  difference  in  temperature  is  greater  the 
loss  of  heat  by  radiation  is  proportionately  greater.  In  cal- 
culating the  number  of  square  feet  of  pipe  surface,  bear  in 
mind  that  the  outer  surface  of  the  pipe  is  meant.  The  re- 
sults of  some  experiments  given  under  "Heating"  in  Ency- 
clopedia Brittanica  indicate  that  cast-iron  pipe  radiates  the 
heat  about  50  per  cent,  faster  than  wrought-iron  pipe. 

TABLE  XII. 

LOSSES  BY  FRICTION  AND  RADIATION  IN   DELIVERING  1,000  LBS.  OF 
STEAM  PER  HOUR  THROUGH  A  BARE  WROUGHT  IRON  PIPE  100 

FT.  LONG,  TERMINAL  GAGE  PRESSURE  75  LBS. 
Nominal 

Inside  Diam.  Lbs.  of  Steam  Lost  per  Hr.  per  100  Lin.  Ft. 

of  Pipe  in  Ins. 
i 


By  Friction. 

By  Radiation. 

Total. 

177.7 

22.9 

200.6 

58.2 

29.0 

87.0 

234 

33-2 

56.4 

5-6 

41.4 

47-0 

1.8 

50.1 

51-9 

0.7 

61.1 

61.8 

0.3 

69.8 

70.1 

O.2 

78-5 

78.7 

NOTE. — The  loss  due  to  friction  varies  as  the  cube  of  the  number 


STEAM  AND  COMPRESSED  AIR  PLANTS.  61 

of  pounds  of  steam  per  hour.  Hence  divide  the  delivery  steam  in 
Ibs.  per  hr.  by  1,000  (1,000  being  the  basis  of  the  table),  cube  the 
quotient  and  multiply  the  quantities  in  column  two  thereby.  Thus 
if  a  3-in.  pipe  must  deliver  2,000  Ibs.  of  steam  per  hour,  we  have, 
2,000  -7-  1,000  =  2,  and  cubing  this  2  we  have  8,  which  multiplied 
by  the  0.7  (in  column  two  opposite  3-in.)  gives  5.6  Ibs.  of  steam 
lost  per  hr.  per  100  ft.  of  3-in.  pipe  due  to  friction.  The  loss  by  ra- 
diation is  the  same,  regardless  of  the  velocity  of  the  steam  in  the 
pipe. 

TABLE  XIII. 

Abstracted  from  an  excellent  paper  on  "Tests  of  Steam  Pipe  Cov- 
erings," by  Geo.  H.  Barrus,  in  Trans.  Am.  Soc.  M.  E.,  1902. 


|X      o  a  £o       £.S£!D  |0- 

3*3     w        *°  «5      '^c~     »*£  w  a|^ 
J^~      ^.S4     ^8  £?»c  •  •"£ 

***  "C  «rJ  OT  CM          "^   ^       •   <D   $*   *•* 

Pipe  Covering.  ^c^     ^  £>>>       ^o      ^  d'^'a 

N.  Y.  Air  Cell  (asbestos)     2      i  3.22        12.32        26        187 

Cast's  Air  Cell  (asbestos)     2      15/16      3.77        10.56       23        198 

Carey's  Moulded    2      i  5.77         8.64       20        192 

Asbesto-sponge   2      i  7.25         8.64        . .        194 

Asbestocel   2        %         5.10         9.60       22        182 

Magnesia    '. 2      i  3.17        40        143 

Asbesto-sponge  (48  lams.)     2      i  6.00        19.20        37        143 

Asbestos,  Navy  brand...     2      i^          3.69        18.24        35        151 
Asbestos,  Navy  brand...   10      i^          12.60        66.0        25          97 

Magnesia   10      13/16    17.88       62.7        24         88 

Asbesto-sponge  felt  10      i^          28.55        73-3        28         70 

Asbesto-sponge  felt  10      13/16    24.47        54-O       21          75 

Bare  iron  pipe 2      750 

According  to  Mr.  Barrus,  the  number  of  Ib.  degs.  (or 
B.  T.  U.)  of  heat  radiated  through  a  pipe  covering  is  in- 
versely proportional  to  the  thickness  of  the  covering  raised 
to  the  y%  power ;  according  to  H.  G.  Stott,  the  heat  radiated 


62         ROCK  EXCAVATION— METHODS  AND  COST. 

is  inversely  proportional  to  the  square  root  of  the  thickness 
of  the  covering.  The  heat  losses,  given  in  the  last  column 
of  Table  XIII.,  are  for  a  difference  of  temperature  of  250° 
F.  between  the  steam  and  the  outside  air ;  for  any  other  dif- 
ference in  temperature  the  heat  loss  is  proportional  to  the 
ratio  of  the  differences  in  temperature.  The  heat  losses 
are  given  per  square  foot  of  the  outside  surface  of  the  pipe ; 
but  to  be  truly  scientific  they  should  be  given  per  square  foot 
of  the  outside  surface  of  the  pipe  covering.  However,  for 
the  tests  of  pipe  covering  made  on  a  2-in.  pipe,  the  results 
show  a  slightly  higher  heat  loss  than  would  occur  on  larger 
pipes,  so  that  the  tabular  data  are  on  the  side  of  safety. 

Since,  according  to  Table  V.,  i  Ib.  of  steam  of  75  Ibs.  pres- 
sure contains  1,179  Mb.  degs.  of  heat  energy  from  water  at 
32°,  or  1,151  Ib.  degs.  from  water  at  60°,  we  have  simply  to 
divide  the  loss  of  heat  expressed  in  Ib.  degs.  by  1,150  to  get 
the  number  of  pounds  of  steam  lost  in  a  pipe  line  per  hour. 
At  70  Ibs.  gage  pressure  the  loss  is  750  Ib.  degs.  per  sq.  ft. 
of  bare  pipe  surface ;  hence  750  -f-  1,150  =  0.66  Ibs.  of  steam 
per  sq.  ft.  per  hr.  Roughly  speaking,  therefore,  an  uncovered 
pipe  loses  2-3  Ib.  of  steam  per  sq.  ft.  per  hr.  The  following 
table  gives  the  area  in  square  feet  of  100  ft.  of  pipe: 
TABLE  XIV. 

r                    i    M-i  r  i    «4-i  r  i    M-I 

J3°  6  13     °  |  3° 

o  **"*  *3  i)*4"  *3  4>  **" 

4,             3  d  <u  3  d  <u  3d 

jo               «  u:  3  £  *~  ?a  £  us 

t/3  ^      r*1,  c/i  13      o  c/5  £3/-\ 

.s         °  §        .s          °  §         .s         °  § 

*0    M-. 


s 

.    0 

•H 

c 

.  o 

.a 

.    0 

C    tn 

4n     o>     0> 

14 

"*       (_)       p| 

*[s& 

cr  45  'S* 

yz 

22.2 

75-2 

6 

173-3 

y± 

27-5 

3 

91.7 

7 

198.0 

I 

344 

3/2 

104.7 

8 

225.2 

iy4 

43-5 

4 

117.8 

9 

250.0 

1/2 

49-8 

4/2 

130.7 

10 

281.7 

2 

62.1 

5 

159.0 

Since  the  heat  loss  in  uncovered  pipe  is  about  2-3  Ib.   of 


STEAM  AND  COMPRESSED  AIR  PLANTS.  63 

steam  per  hr.  per  sq.  ft.  of  pipe  surface,  we  have  merely  to 
multiply  the  number  opposite  the  pipe  of  given  size  in  Table 
XIV.  by  2-3  to  determine  the  approximate  loss  of  steam. 
In  a  24 -in.  pipe  the  area  is  27.5  sq.  ft.  per  100  lin.  ft.  of  pipe ; 
hence  the  steam  loss  is  2-3  X  27.5  =  18.3  Ibs.  of  steam  per 
hour.  If  the  pipe  is  150  ft.  long  the  loss  is  27^  Ibs.  of  steam 
per  hour,  due  to  radiation,  at  least  80  per  cent,  of  which  loss 
can  be  saved  by  using  a  pipe  covering  little  more  than  an  inch 
thick.  Pipe  coverings  can  be  bought  in  short  lengths  that 
slip  like  sleeves  over  the  pipe.  For  outdoor  use  the  cover- 
ing should  be  of  some  flexible  variety,  preferably  of  asbestos 
fibre  (not  moulded  hard  with  plaster),  wrapped  with  water- 
proofed canvas.  A  fair  idea  of  the  prices  may  be  had  by  in- 
specting Table  XIII. 

In  a  compressed  air  pipe  line  there  is  no  loss  of  energy  by 
heat  radiation ;  hence  the  larger  the  pipe  the  greater  its  effi- 
ciency in  conveying  the  air  without  reducing  its  final  pres- 
sure at  the  drill.  But  in  a  steam  pipe  line  the  larger  the  pipe 
the  greater  the  loss  by  heat  radiation,  whereas  the  smaller 
the  pipe  the  greater  the  loss  by  friction.  Hence  for  any  given 
quantity  of  steam  to  be  delivered  per  hour  there  is  just  one 
size  of  pipe  that  will  give  a  minimum  loss  of  energy,  which 
may  be  calculated  from  the  data  given  in  this  chapter. 

Flow  of  Air  Through  Pipes.— Tables  XV.  to  XVII.  are 
based  upon  D'Arcy's  formula.  Table  XV.  gives  the  number 
of  cubic  feet  of  free  air  delivered  per  minute  through  a  pipe 
loo  ft.  long  without  any  loss  of  pressure.  Table  XVI.  gives 
the  factors,  F.,  to  be  used  for  different  lengths  of  pipe.  Table 
XVII.  gives  the  multipliers,  M,  to  be  used  to  determine  the 
loss  of  pressure.  The  following  formulas  are  to  be  used 
with  these  tables :  Q 

: 


(1)  Q  =  LXFXM  FXM 

Q  O 

(2)  M    =  (A\    F  ~-    — 

L  X  F  '  L  X  M 

Q  =  cu.  ft.  of  free  air  discharged  per  min. 
L  =  factor  given  in  Table  XV. 


64          ROCK  EXCAVATION— METHODS  AND  COST. 

F  =  factor  given  in  Table  XVI. 
M=      "         "        "      "       XVII. 

Example  i.  Given  a  4-in.  pipe,  600  ft.  long,  initial  air  pres- 
sure 60  Ibs.,  required  to  discharge  1,200  cu.  ft.  of  free  air 
per  min.,  what  will  be  the  terminal  pressure? 

By  Table  XV.,  under  4-in.  pipe  and  opposite  60  Ibs.,  we 
find  L  =  1,535. 

By  Table  XVI.,  for  600  ft.,  F  =  0.408. 

Hence,  M  =    .,  *~p  =  1,200 ^ 

LXF         1,535x0.408 

Now  by  Table  XVII.,  opposite  60  Ibs.  pressure  and  under 
4  Ibs.  reduction,  we  find  M  =  1.89,  so  that  the  loss  of  pres- 
sure being  4  Ibs.  we  have  a  terminal  pressure  of  56  Ibs. 

Example  II.  Given  a  6-in.  pipe,  2,000  ft.  long,  initial  pres- 
sure 80  Ibs.,  terminal  pressure  70  Ibs.,  what  will  be  the 
volume  discharged? 

By  Table  XV.,  under  6-in.  pipe  and  opposite  80  Ibs.,  we 
find  L  =  4,971. 

By  Table  XVI,  for  2,000  ft.  length,  F  =  0.224. 

By  Table  XVII.,  under  10  Ibs.  reduction  and  for  80  Ibs. 
pressure,  we  find  M  =  2.82. 

Q  =  LXFXM  =  4,971  x  0.224  x  2.82  =  3,140  cu. 

ft.  per  min. 

TABLE  XV. 
GIVING  FACTOR  L. 

Nominal  Diameter  of  Pipes  in  Inches. 
Gage,  , * 


Lbs.   i"    iy2"    2"     2Y2"       3"      sW    4"     5"    6"     7"      8"      10" 

50  38.96  122.4  2434  396.3  701-5  1030  1430  2558  4114  5993  8312  14910 

60  41.83  131.4  261.1  425.4  752.9  1105  1535  2747  4416  6433  8920  16000 

70  44.53  139.9  278.0  452.9  801.8  1176  1634  2925  4701  6848  9499  17030 

80  47.08  147.9  294.0  478.8  847.6  1244  1728  3091  4971  7240  10040  18000 

90  49.54  155.6  309.3  503.8  891.8  1307  1817  3253  5230  7619  10560  18940 

100  51.88  163.0  324.0  527.5  933.8  1370  1904  3407  5477  7979  11050  19850 

1 10  54.10  169.9  337-8  550.1  973.9  1429  1985  3552  5712  8320  11530  20690 

125  57.15  179-5  356.8  581.3  1028  1510  2097  3754  6034  8789  12180  21860 

150  62.10  195.1  387.8  631.7  1117  1641  2280  4080  6558  9553  13240  23760 


STEAM  AND  COMPRESSED  AIR  PLANTS. 


65 


TABLE  XVI. 

GIVING 

FACTOR  F. 

Length,  feet. 

Multiplier  F. 

Length,  feet. 

Multiplier 

100 

I.O 

6000 

0.129 

200 

0.707 

7000 

0.119 

300 

0-577 

8000 

O.I  12 

400 

0.500 

9000 

0.105 

500 

0.447 

IOOOO 

0.100 

600 

0.408 

12,000 

0.0912 

750 

0-365 

15,000 

0.0817 

IOOO 

o  116 

1250 

0.283 

***  JW 

moo 

0.258 

*  JW 

2OOO 

w.^»^*-r 

O  224 

2500 

\J.£l£ii+ 

0.200 

3000 
3500 


0.169 
0.158 
0.141 


TABLE  XVII. 


Initial 
Gage 
Pressure. 
Pounds. 

50  
60  
70  
80  
90  

R 

i 

0.984 
0.986 
0.988 
0.989 
0.990 
0.991 
o.99'2 
0-993 
0.994 

GIVING  FACTOR  M. 

eduction  of  the  final  pressure  in  pounds  per  square  inch. 
234            6          8          10         12        14          16         18           20 

37       1.65         .87      2  22       2  48       2  67            .  .          .                                

.37     1.66       .89    2.24     2.52     2.74      
.38    1.67      .90    2.27    2.56    2.79    2.97    3.12    3.24     

.38     1.67       .91     2.29     2.59     2.82     3.02     3.19'     3.32.  3.43     3.53 
.38     1.68       .92     2.31     2.61     2.86    3.06     3.24    3.39     3.51     3.61 
.39     1.68       .93     2.32    2.63     2.88     3.10     3.28    3.44     3-57     3-69 
•  39     1-69       -93     2-33     2.64     2.90     3.13     3.32     3.48     3.63     3-75 
.39     1.69       .94     2.34    2.66     2.93     3.16     3.36    3.54    3.69     3.83 
.39     1.70       .95     2.36     2.69     2.97     3.21     3.42     3.61     3.77     3.92 

100  

no  

125  
150  

Fuel  and  Steam  Boiler  Efficiency. — Steam  boilers  are  com- 
monly rated  as  having  so  and  so  many  horse-power  capacity. 
This  is  a  very  misleading  and  unsatisfactory  way  of  rating 
a  boiler,  for  the  horse  power  of  work  that  a  boiler  can  do 
depends  entirely  upon  the  kind  of  engine  to  which  the  steam 
goes.  A  boiler  that  supplies  1,600  Ibs.  of  steam  per  hour  to 
compound  condensing  engine  using  16  Ibs.  of  steam  per 
H.  P.,  evidently  develops  100  H.  P. ;  yet  if  this  very  same 
boiler  is  made  to  feed  an  ordinary  single  cylinder  non-con- 
densing engine  using  40  Ibs.  of  steam  per  hour,  it  will  de- 
velop 1600  -r-  40  =  40  H.  P.  In  buying  a  boiler,  therefore. 


66          ROCK  EXCAVATION— METHODS  AND  COST. 

be  sure  to  secure  the  manufacturer's  guarantee,  not  of  its 
horse  power,  but  of  its  steam  capacity  in  pounds  of  steam 
per  hour  at  a  given  gage  pressure  (say,  70  Ibs.  per  sq.  in.), 
using  a  fuel  of  a  kind  stated  in  the  guarantee.  The  Amer- 
ican Society  of  Mechanical  Engineers  has  recommended  that 
wherever  the  word  horse  power  is  used  in  reference  to  boil- 
ers, it  shall  mean  30  Ibs.  of  water  evaporated  from  100°  F. 
to  steam  having  a  gage  pressure*  of  70  Ibs.  per  sq.  in.  under 
average  firing  without  forcing  the  boiler,  and  by  forcing  the 
same  boiler  should  be  capable  of  evaporating  1-3  more  steam 
per  hour  than  its  ordinary  rating;  that  is,  a  100  H.  P.  boiler 
(30  Ibs.  steam  per  hr.  per  H.  P.)  should  be  capable  of  de- 
veloping 133  H.  P.  if  forced.  Unfortunately  manufacturers 
usually  pay  no  attention  to  this  suggested  rating,  and 
.perhaps  they  can  hardly  be  blamed,  because  if  it  were  al- 
ways followed  we  should  see  at  times  a  100  H.  P.  boiler  used 
to  run  a  200  H.  P.  compound  condensing  engine,  while  at 
other  times  the  same  100  H.  P.  boiler  would  be  used  to  run 
a  100  H.  P.  non-condensing  single  engine. 

By  careful  tests  it  is  easy  to  ascertain  how  many  Ib.  degs. 
can  be  developed  by  I  Ib.  of  any  fuel  burning  under  perfect 
conditions.  Thus  I  Ib.  of  perfectly  pure  carbon  will  develop 
15,000  Ib.  degs. ;. that  is,  it  will  raise  the  temperature  of 
15,000  Ibs.  of  water  i°,  or  150  Ibs.  of  water  100°.  Coal  is 
never  entirely  pure  carbon,  but  contains  some  ash  and  other 
materials.  All  mechanical  engineers'  handbooks  contain 
tables  of  the  heating  value  of  different  kinds  of  fuel,  with 
which  it  is  well  to  be  familiar  whenever  there  is  a  choice  of 
fuels. 

When  coal  is  burned  under  a  boiler  a  large  percentage  of 
its  heat  passes  up  the  chimney  in  the  gases  and  is  lost ;  and 
in  addition  to  this  loss  the  boiler  itself  radiates  heat  con- 
stantly. The  greater  part  of  the  loss  occurs  in  the  heat  that 


*  The  atmosphere  has  a  pressure  of  14.7  Ibs.  per  sq.  in.,  and  since  a  steam 
gage  shows  the  steam  pressure  above  atmospheric  pressure,  \ve  must  add  14.7 
to  the  gage  pressure  to  get  the  "absolute  pressure." 


STEAM  AND  COMPRESSED  AIR  PLANTS.  67 

goes  up  the  chimney.  In  large,  well  designed  boilers,  proper- 
ly protected  by  asbestos  or  similar  covering,  the  coal  burned 
will  develop  steam  to  about  85  per  cent,  of  the  full  heat 
value  of  the  fuel ;  the  efficiency  of  the  boiler  and  furnace  is 
then  85  per  cent.  In  locomotive  boilers  where  forced  draft 
is  used,  firing  not  of  the  best  and  boiler  exposed  to  moving 
air,  the  efficiency  is  often  as  low  as  45  per  cent.  The  effi- 
ciency of  a  good  boiler  of  moderate  size  (100  H.  P.),  well 
housed,  is  ordinarily  about  75  per  cent.  A  small  (20  H.  P.) 
boiler  exposed  to  the  wind  has  an  efficiency  of  55  to  60  per 
cent,  when  not  forced. 

If  a  small  boiler  is  used  to  run  one  drill,  the  boiler  must 
always  have  up  enough  steam  to  keep  the  drill  running  at 
nearly  full  capacity;  but  when  the  drill  is  stopped,  during 
the  changing  of  bits,  moving,  etc.,  there  is  a  waste  of  steam, 
because  the  period  of  stoppage  is  not  long  enough  to  permit 
the  fireman  to  make  any  material  change  in  the  firing  and  in 
the  draft.  Hence  one  single  drill  (3^  in.)  must  be  counted 
upon  as  using  about  250  Ibs.  of  steam  per  hour  (see  page 
58).  A  i-in.  steam  pipe  200  ft.  long,  if  not  covered,  will 
lose  nearly  50  Ibs.  of  steam  per  hour  by  condensation  (and 
often  as  much  more  by  leakage),  thus  making  a  total  steam 
consumption  of  250  +  5°  —  3°°  Ibs.  per  hour,  due  to  the 
drill  and  the  pipe  line.  If  I  Ib.  of  the  coal  will  develop  14,000 
Ib.  degs.,  and  if  the  small  exposed  boiler  has  an  efficiency 
of  58  per  cent.,  we  have  14,000  X  58  per  cent.  =  8,120  Ib. 
degs.,  which  divided  by  1,150  (the  Ib.  degs.  required  to  pro- 
duce I  Ib.  of  steam  at  ordinary  pressures),  gives  about  7 
Ibs.  of  steam  produced  by  i  Ib.  of  coal.  Therefore,  300  -h 
7  =  43  Ibs.  of  coal  required  per  hour  to  supply  steam  for 
the  drill  and  pipe  line.  We  have  still  to  add  the  loss  of  fuel 
when  the  fire  is  drawn  at  night,  as  well  as  the  loss  of  radi- 
ated heat  during  the  starting  of  the  fire  in  the  morning,  and 
leakage  losses.  Not  less  than  150  Ibs.  of  coal  per  day  are 
thus  consumed  in  a  small  boiler,  bringing  the  total  coal  con- 
sumption up  to  580  Ibs.  of  coal  for  running  the  one  drill 


68         ROCK  EXCAVATION— METHODS  AND  COST. 

one  lo-hr.  shift.  Where  two  drills  are  run  by  steam,  the 
consumption  of  coal  per  drill  is  somewhat  less.  Where  a 
large  number  of  drills  are  in  use,  all  are  seldom  running  at 
the  same  time,  but  at  no  time  is  the  boiler  entirely  without 
some  drills  drawing  steam  from  it.  Under  such  conditions, 
and  where  the  main  pipe  line  is  lagged,  each  drill  will  require 
about  250  Ibs.  of  coal  per  lo-hr.  shift  under  average  con- 
ditions. Knowing  the  number  and  size  of  drills,  the  size  of 
steam  pipes,  the  character  of  lagging  around  the  pipes,  the 
depth  of  drill  holes  and  kind  of  rock,  it  is  possible  to  esti- 
mate the  coal  consumption  per  drill  with  considerable  ac- 
curacy by  applying  the  data  given  in  this  chapter  and  in  the 
next  chapter. 

Merits  of  Compressed  Air. — A  compressed  air  plant  was 
recently  installed  at  a  large  stone  quarry  where  drills  and 
channelers  had  formerly  been  run  by  steam  direct  from  a 
large  number  of  small  boilers.  When  the  compressed  air 
plant  was  installed  the  coal  consumption  was  reduced  from 
50  tons  per  day  to  15  tons  per  day.  Due  to  the  higher  and 
more  even  pressure  of  the  air  (as  compared  with  the  steam 
from  the  small  boilers),  fewer  drills  and  channelers  were 
needed,  because  each  did  more  work  than  before.  More- 
over, there  were  no  delays  in  the  morning,  getting  up  steam, 
as  is  usually  the  case  where  a  large  number  of  small  boilers 
are  operated.  This  excellent  and  remarkable  result  could 
have  been  accomplished  at  less  expense  by  installing  a  cen- 
tral steam  boiler  plant  and  using  lagged  steam  pipes.  The 
steam  pipes  would  have  required  expansion  joints  and  traps 
for  draining  off  water  of  condensation  similar  to  those  in 
the  air  pipe  system.  This  plant  was  widely  advertised  as 
proving  conclusively  the  advantage  of  using  compressed  air 
instead  of  steam  in  drills.  What  it  really  proves  is  that  a 
central  power  plant  is  far  more  economic  than  a  large  num- 
ber of  small  plants.  We  have  seen  that  the  efficiency  of 
small  boilers  is  often  45  per  cent,  or  lower,  as  compared  with 
the  85  per  cent,  efficiency  of  large  boilers.  We  have  also 


STEAM  AND   COMPRESSED  AIR  PLANTS.  69 

seen  that  a  small  boiler  supplying  one  or  two  drills  must  al- 
ways carry  enough  steam  to  keep  both  drills  going  at  their 
full  steam  consumption,  in  spite  of  the  fact  that  the  drills  are 
not  working  more  than  40  to  70  per  cent,  of  the  time ;  where- 
as with  a  large  central  plant  the  drills  "average  up,"  some 
running  while  others  are  not,  thus  greatly  reducing  the 
average  daily  coal  consumption.  Compressed  air  has  many 
advantages  over  steam  for  operating  drills,  but  a  reduction  in 
the  coal  bill  is  not  one  of  them  (in  spite  of  the  general  belief 
to  the  contrary)  if  a  fair  comparison  is  made  between  a  cen- 
tral steam  plant  with  covered  pipes  and  a  central  compressor 
plant. 

Compressed  air,  however,  possesses  several  advantages 
distinctly  its  own,  which  may  be  enumerated  as  follows :  ( I ) 
It  does  not  rot  the  hose  from  the  pipe  to  the  drill,  and  a 
much  cheaper  hose  may  be  used  and  consequently  a  longer 
hose  than  with  steam.  (2)  Less  oil  is  required  to  keep  the 
drill  lubricated.  (3)  In  warm  weather  the  exhaust  air  makes 
working  around  the  drill  comfortable.  (4)  A  trench  or 
quarry  pit  is  not  filled  with  steam,  making  it  difficult  at 
times  to  see.  (5)  There  is  no  danger  of  injuring  the  drill 
itself  by  sudden  expansion  due  to  heat.  (6)  There  are  no 
pipes  to  thaw  out  in  winter  due  to  condensed  water  care- 
lessly allowed  to  collect.  (7)  Plug  drills  can  be  used  for 
block  holing,  plug  and  feathering,  etc.  (8)  The  air  can  be 
used  for  blowing  the  sludge  and  water  out  of  a  hole  before 
charging.  (9)  The  air  can  be  used  for  forcing  a  jet  of 
water  into  a  hole  alongside  of  the  drill-rod.  (10)  The  ma- 
chine being  cool  is  easily  handled,  (n)  Water  power  may 
be  used  for  compressing  the  air. 

Efficiency  of  the  Jerome  Reservoir  Plant. — There  are  few 
records  of  careful  tests  of  the  efficiency  of  boilers,  engines 
and  air  compressors  of  a  single  plant.  In  Saunders's  "Com- 
pressed Air  Information,"  p.  193,  a  very  complete  record  is 
given  of  a  lo-hr.  test  of  a  plant  in  operation,  supplying  air 
to  14  drills,  14  derrick  engines  and  three  small  pumps.  The 


70          ROCK  EXCAVATION— METHODS  AND  COST. 

test  was  made  by  George  W.  Vreeland    and    Charles    M. 
Younglove. 

The  plant  is  used  in  excavating  the  site  of  the  Jerome 
Park  Reservoir,  N.  Y.  (still  under  construction,  1904),  and 
consists  of  one  Ingersoll-Sergeant  Corliss  cross-compound 
condensing  air  compressor  plant,  receiving  steam  from  two 
Hogan  boilers,  each  of  270  H.  P.  (nominal).  The  follow- 
ing are  some  of  the  data  of  the  test : 

Steam  gage,  Ibs.  per  sq.  in 1 16.5 

Coal  used  per  hour,  Ibs 928 

Dry  steam  per  hour,  Ibs 8,274 

Efficiency  of  boiler  78.1% 

Steam  per  I.  H.  P.,  Ibs 17.36 

Total   I.   H.   P.  of  engines 468 

Total  D.  H.  P.  of  engines 402 

Mechanical  efficiency  of  engines 86% 

Thermal  efficiency  of  compression 82% 

Free  air  per  min.  per  I.  H.  P.,  cu.  ft 6 

Gage  pressure  of  compressed  air,  Ibs. 67.5 

Heat  supplied  to  engine  per  hr.,  Ib.  degs 9,634,246 

Heat  utilized  by  engine-  per  hr.,  Ib.  degs 1,177,437 

This  is  an  average  size  compressor  plant,  capable  of  car- 
rying at  least  35  drills  (3>4-in.)  ;  and  if  it  were  loaded  with 
35  drills,  each  drill  would  be  charged  with  265  Ibs.  of  coal, 
for  a  lo-hr.  run,  or  276  Ibs.  of  steam  per  hour,  or  with  13.4, 
I.  H.  P.  of  compressor  engine.  Particular  note  should  be 
taken  of  the  heat  efficiency  of  the  engine,  which  may  be  cal- 
culated by  dividing  the  1,177,437  Ib.  degs.  by  the  9,634,246 
Ib.  degs.,  the  quotient  being  12.3  per  cent.  Those  who  have 
not  made  a  careful  study  of  the  compressed  air  problem 
would  be  misled  by  the  statement  that  the  efficiency  of  com- 
pression is  82  per  cent.,  and  would  be  apt  to  think  that  this 
was  for  the  engine  and  compressor  plant.  In  fact  the  true 
heat  efficiency  of  this  plant  was  12.3  X  -82  =  10.086  per 
cent.,  a  trifle  more  than  10  per  cent. — which  checks  closely 
with  the  calculations  in  the  fore  part  of  this  chapter. 

Gasoline  Air  Compressors. — Where  not  more  than  three  or 
four  drills  are  to  be  operated,  probably  no  power  can  equal 


STEAM  AND  COMPRESSED  AIR  PLANTS.  71 

compressed  air  generated  by  gasoline.  One  pint  of  gasoline 
per  hour  per  brake  horse  power  (B.  H.  P.)  of  gasoline 
engine  may  be  counted  upon  as  the  average  consumption.  It 
will  require  about  12  H.  P.  to  compress  air  for  each  drill 
(3^4-in.  size)  ;  hence  12  pints,  or  i^  gals.,  of  gasoline  will 
be  required  per  hour  per  drill  while  actually  drilling.  Since 
gasoline  air  compressors  are  self  regulating,  when  the  drill 
is  not  using  air  very  little  gasoline  is  burned  by  the  gasoline 
engine  driving  the  compressor.  If  the  drill  is  actually  drill- 
ing two-thirds  of  the  working  shift,  we  may  safely  count 
upon  using  about  I  gal.  of  gasoline  per  hour  of  shift  per  drill, 
or  8  gals,  per  shift  8  hrs.  long.  If  gasoline  is  worth  15  cts. 
per  gal.,  delivered  at  the  engine,  one  drill  consumes  only 
$1.20  worth  of  gasoline  per  shift  of  8  hrs.  In  shaft  sinking, 
tunnel  work  and  the  like,  as  will  be  shown  later,  a  drill  is 
often  idle  two-thirds  of  the  shift,  so  that  the  gasoline  con- 
sumption would  be  still  less. 

A  gasoline  compressor  possesses  other  very  important 
economic  advantages  over  a  small  steam-driven  plant.  First, 
there  is  the  saving  in  wages  of  firemen;  for,  once  started, 
a  gasoline  engine  runs  itself.  Second,  there  is  the  saving  in 
hauling  or  pumping  of  water  and  the  hauling  of  fuel.  Third, 
the  cost  of  gasoline  is  often  less  than  the  cost  of  coal  for 
operating  a  small  plant.  The  Golden  Wave  Mine,  Congress, 
Ariz.,  used  a  30  H.  P.  gasoline  driven  compressor  (Fair- 
banks-Morse) for  sinking  an  incline,  at  a  cost  that  was  re- 
markably low.  I  believe  this  type  of  plant  is  destined  to  find 
an  increasing  field  of  usefulness.  It  is  especially  adapted  for 
rock  trench  excavation  in  cities,  for  tunnel  work  and  for 
open  cuts  where  only  a  few  drills  are  operated. 


CHAPTER  V. 

THE  COST  OF  MACHINE  DRILLING. 

Cost  Factors, — The  items  that  go  to  make  up  the  cost  of 
power  drilling  are : 

1.  Wages  of  driller  and  helper. 

2.  Proportionate  part  of  wages  of  engine  and  boiler  crew. 

3.  Fuel. 

4.  Sharpening  drills,  including  transportation  to  and  from 

shop. 

5.  Repairs  and  renewals. 

6.  Interest  and  depreciation  of  plant  distributed  over  the 

shifts  actually  worked. 

7.  Water  and  oil. 

8.  Proportionate  part  of  general  expenses,  such  as  salaries 

of  superintendent,  office  employees,   rent,  etc. 

9.  Installation  of  plant,  including  freight,  hauling,  setting 

up,  dismantling,  etc. 

I  have  enumerated  these  items  because  it  is  a  common 
error  to  overlook  one  or  more  of  them;  and  for  the  same 
reason  I  will  now  give  the  factors  that  determine  the  num- 
ber of  feet  of  hole  drilled  per  shift : 

1.  Character  of  rock,  including  resistance  to  drilling,  pres- 
ence of  seams,  rapidity  of  formation  of  sludge  or  dust,  etc. 

2.  The  percentage  of  time  required  to  change  bits,  to  shift 

the  drill  and  to  set  up. 

3.  The  depth  of  hole. 

4.  The  size  of  bits,  top  and  bottom. 

5.  The  use  of  water  jets  for  removing  sludge. 

6.  The  form  and  sharpness  of  the  bits. 

7.  The  direction  of  the  hole,  up,  horizontal  or  down. 

8.  The  percentage  of  time  lost  in  blasting,  breakdowns, 

sticking  of  bits,  etc. 

72 


THE   COST   OF  MACHINE   DRILLING.  73 

9.  The  pressure  of  the  air  or  steam  at  the  drill. 

10.  The  size  of  the  drill  cylinder. 

In  publishing  records  of  drilling  costs,  every  one  of  the 
foregoing  factors  should  be  given,  yet  it  is  rarely  that  half 
of  them  are  recorded.  Indeed  it  is  the  custom  to  state  merely 
the  kind  of  rock,  the  name  of  the  drill,  and  the  cost  in 
cents  per  foot  of  hole  drilled  without  any  statement  as  to 
rates  of  wages,  price  of  fuel,  or  in  fact  any  of  the  data  needed 
to  form  an  intelligent  estimate  of  the  applicability  of  the  in- 
formation to  other  work. 

Percentage  of  Lost  Time. — In  operating  machines  of  any 
kind  the  percentage  of  lost  time  is  a  factor  that  should  re- 
ceive the  moct  careful  consideration.  Notwithstanding  the 
self-evidence  of  this  fact,  I  have  looked  in  vain  for  published 
records  showing  the  average  time  lost  in  setting  up,  changing 
bits,  cleaning  hole,  etc.  Fearing  that  my  own  records  of 
these  extremely  important  items  might  not  cover  a  suffi- 
ciently wide  range  of  conditions,  I  prepared  blanks  which 
I  sent  to  a  number  of  contractors  and  mine  managers.  I 
was  not  surprised  to  receive  some  answers  to  the  effect 
that  conditions  were  so  variable  as  to  make  such  records 
of  no  practical  value.  Now,  it  was  precisely  for  the  purpose 
of  determining  the  range  of  conditions  that  these  blanks  were 
sent  out.  Indeed,  no  perfect  picture  of  conditions  can  be 
given  except  by  the  filling  in  of  just  such  blanks.  They  tell 
at  a  glance  whether  the  rock  was  easy  to  drill  or  hard; 
whether  the  sludge  cushioned  the  blow  of  the  bit  or  not; 
whether  the  drill  crew  was  lazy  or  not,  and,  in  a  word,  just 
what  the  conditions  of  operation  were,  so  far  as  drilling  was 
concerned. 

The  most  serious  loss  of  time  in  machine  drilling  is  the 
time  lost  in  changing  bits  and  pumping  out  the  hole;  for, 
with  a  2-ft.  feed  screw  (which  is  the  ordinary  length),  a  new 
drill  must  be  inserted  for  every  2  ft.  of  hole  drilled.  It 
takes  from  4  to  16  minutes,  to  drill  2  ft.  of  hole,  counting 
the  actual  time  that  the  drill  is  striking,  and  it  ordinarily 


74  ROCK  EXCAVATION— METHODS  AND  COST. 
takes  from  2  to  10  minutes  to  change  bits  and  pump  out  the 
hole.  I  have  often  timed  work  where  9  minutes  were  spent 
in  drilling,  followed  by  9  minutes  lost  in  changing  bits. 
Counting  no  other  time  losses,  then,  half  the  available  time 
was  lost  in  the  operation  of  changing  bits.  From  the  writ- 
ten reports  that  I  have  received,  I  am  certain  that  few  min- 
ing men  and  fewer  contractors  have  ever  given  this  phase 
of  drilling  any  consideration  at  all,  although,  in  my  judg- 
ment, it  is  often  the  cause  of  a  loss  where  there  should  be  a 
profit.  In  all  the  literature  on  the  subject  of  drilling,  I  have 
been  unable  to  find  a  single  mention  of  the  importance  of 
timing  drilling  operations  with  the  minute  hand  of  the  watch. 
Where  holes  are  drilled  to  a  depth  of  10  ft.  or  more,  the 
drill  steel  becomes  so  heavy  that  change  of  bit  is  an  opera- 
tion usually  requiring  3  minutes.  When  done  properly,  the 
driller  starts  to  raise  the  drill  with  the  feed  screw  and  at 
the  same  instant  the  drill  helper  begins  to  loosen  the  chuck 
with  his  wrench.  Without  any  great  effort  these  two  opera- 
tions are  finished  at  the  same  time,  requiring  about  I  minute. 
The  pumping  out  of  the  hole  with  the  sludge  pump  can  be 
done  by  the  drill  helper  in  I  minute,  or  less,  but  I  have 
frequently  seen  deliberate  workers  take  2  minutes  or  more. 
The  drill  helper  then  puts  a  new  drill  into  the  hole  and  enters 
its  shank  in  the  chuck ;  as  soon  as  this  is  done  the  driller 
should  begin  to  feed  the  drill  forward,  and  the  drill  helper 
should  at  once  tighten  the  chuck;  these  operations  taking  I 
to  1^4  minutes.  After  the  first  few  blows  are  struck,  it  is 
often  necessary  to  tighten  the  chuck  again,  consuming  y2  to 
24  minute,  but  this  can  be  obviated  by  using  good  chuck 
bolts  and  by  training  the  men  properly.  The  three  necessary 
operations  (removing  bit,  pumping,  and  putting  in  new  bit) 
can  be  done  with  ease  in  3  to  3^  minutes.  If,  however,  the 
drill  helper  waits  till  the  driller  has  raised  the  drill  steel  be- 
fore he  begins  loosening  the  chuck,  another  minute  may  be 
unnecessarily  added  to  the  time ;  and,  in  a  similar  manner, 
by  deliberation  (which  is  equivalent  to  laziness)  the  two 


THE   COST   OF   MACHINE   DRILLING,  75 

men  may  while  away  6  minutes  or  more  unnecessarily. 
When  shallow  holes  (6  ft.  or  less),  are  to  be  drilled,  the  drill 
steel  is  light  and  there  is  often  little  or  no  sludge  pump- 
ing to  be  done.  In  such  cases  it  is  possible  for  the  driller 
and  his  helper  to  change  bits  in  i  minute,  or  even  less  when 
they  are  rushing  the  work.  So  far  as  the  changing  of  bits  is 
concerned  the  men  should  be  made  to  work  with  a  vim. 
When  men  have  to  exercise  their  muscles  incessantly  for  8  or 
10  hours  there  is  reason  in  taking  a  slow,  steady  gait,  but  in 
machine  work,  muscular  exercise  is  intermittent  and  should 
be  vigorous. 

Next  in  importance  to  the  time  lost  in  changing  bits  is  the 
time  lost  in  shifting  the  machine  from  hole  to  hole.  This, 
again,  is  a  factor  not  touched  upon  by  writers,  in  spite  of  its 
importance,  especially  in  drilling  shallow  holes.  To  move 
a  tripod  from  one  hole  to  the  next  and  set  up  again  ready  to 
drill,  seldom  consumes  less  than  7  minutes,  even  when  the 
two  men  are  working  rapidly,  when  the  distance  to  move  is 
short,  and  when  the  rock  floor  is  level  and  soft.  When, 
however,  the  rock  floor  is  irregular  and  hard,  requiring  the 
vigorous  use  of  gad  and  pick,  not  only  in  making  holes  for 
the  tripod  leg  points  to  rest  in,  but  requiring,  also,  some  little 
time  in  squaring  up  a  face  for  the  bit  to  strike  upon,  the 
two  men  may  consume  from  30  to  45  minutes,  shifting  the 
machine  and  setting  up,  if  they  work  deliberately.  In  such 
cases  it  is  advisable  to  have  laborers  workinp-  ahead  of  the 
drillers  preparing  the  face  of  the  rock,  leveling  the  site  of 
the  hole,  removing  loose  rock,  etc.  One  can  see  clearly  what 
a  great  saving  in  time  may  thereby  be  effected;  yet,  this 
simple  expedient  is  seldom  adopted;  but  the  driller  and  his 
helper  are  usually  left  to  themselves  in  preparing  the  ground 
for  each  new  set  up.  I  repeat  aeain  that  everv  foreman 
and  manager  of  rock  excavation  should  use  the  minute  hand 
of  his  watch  frequently  (and  at  times  when  he  is  not  ob- 
served), to  determine  exactly  how  much  time  his  men  are 


76         ROCK  EXCAVATION— METHODS  AND  COST. 

losing  in  changing  bits  and  shifting.     He  will  thus  learn 
where  his  employer's  money  is  being  wasted. 

Where  drillers  are  obliged  to  move  long  lengths  of  air  or 
steam  pipe  before  blasting,  or  where  narrow  trenching 
makes  it  difficult  to  shift  the  drill  and  causes  material  delay 
in  advancing  the  steam  pipe  line,  there  are  obviously  other 
sources  of  delay  which  should  be  ascertained  by  careful  tim- 
ing, with  a  view  to  reducing  the  delay  by  some  additional 
expenditure  of  money  if  found  advisable. 

In  seamy  or  soft  rock  where  the  bit  sticks  frequently  in 
the  hole  the  time  lost  from  this  cause  alone  may  be  30  per 
cent. 

Excluding  the  time  required  to  change  bits  for  the  new 
hole,  we  may  say  that  two  men  can  ordinarily  make  a  new 
set  up  with  a  tripod  in  12  to  15  minutes,  if  they  work  rapidly. 
When  the  drill  is  mounted  on  a  column  or  bar,  the  time  re- 
quired to  set  up  the  column  and  get  ready  to  drill  ranges 
from  10  minutes  (when  the  men  are  racing)  up  to  60  min- 
utes (when  the  men  are  loafing).  Men  working  deliberately 
ordinarily  take  about  25  minutes.  From  one  set  up  of  a  col- 
umn, however,  6  to  12  holes  may  be  drilled,  by  shifting  the 
drill  along  the  column.  The  shifting  itself  need  not  take 
more  than  I  to  2  minutes,  but  the  time  required  in  addition 
for  changing  bits  and  cleaning  the  hole  will  not  differ  ma- 
terially from  the  time  above  given  for  tripod  work. 

Tables  XVIII  and  XIX  give  typical  examples  of  actual 
work  in  different  kinds  of  rock  and  in  different  parts  of  the 
United  States.  Part  of  the  data  was  taken  from  my  own 
notes,  but  I  wish  here  to  express  my  thanks  for  most  of 
the  data  to  the  following  mining  and  civil  engineers:  Mr. 
B.  B.  Lawrence,  Mining  Engineer ;  Mr.  E.  C.  Means,  Min- 
ing Engineer ;  Mr.  Alex.  Veitch,  Mining  Engineer ;  Mr.  R. 
Oilman  Brown,  Mining  Engineer;  Mr.  T.  H.  Loomis,  Civil 
Engineer;  Mr.  Walter  Seeley,  Civil  Engineer. 


THE   COST   OF  MACHINE  DRILLING.  77 

TABLE  XVIII. 

AVERAGE  TIME  DRILLING  VERTICAL  HOLES. 
(Drill  mounted  on   a   tripod.) 

ABC         D        K 

Drilling  first  2   ft.,  mins 9  10^  12  8  14 

Cranking  out  and  removing  bit,  mins i  zl/2  i  ilA        *Y> 

Cleaning   out   hole,   mins 3  i  i/4        i  /4 

Putting  in  new  bit  and  cranking  back,  mins...  i  2^  i/4        i  1^2 

Drilling  second   2   ft,,   mins 13  ioj^  ..  ..  14 

Drilling  last  2   ft.,   mins 12  10^  11  6 

Moving  machine  from  hole  to   hole  and  setting 

up    IS  35  ••  12  36 

Air  pressure,  Ibs.  per  sq.  in 70  (?)  80  70  70 

Diameter   of   drill   cylinders,   ins 3%        3/4  31A        3/4        3/4 

Diameter  of  starting  bit,  ins 2l/2       2^/2  3%       2  2^ 

Diameter  of  finishing  bit,  ins i$4        iH        i/4        i/4       2 

Depth  of  hole,    ft 12  6  20  12  6 

Kind  of   rock Lm.       S.  Gr.  Sd.  Tr. 

Length  of  shift,  hrs 10  10  10  10  10 

Ft.  drilled  per  shift 48  96  36 

NOTE. — The  kind  of  rock  designated  by  the  abbreviations  is  as  follows:  Lm., 
limestone;  S.,  sandstone  (hard);  Gr.,  granite;  Sd.,  sandstone  (soft);  Tr.,  trap 
(diabase J. 

TABLE  XIX. 

AVERAGE  TIME  DRILLING  HOLES  IN  A  BREAST. 
(Drill  mounted  on  a  column.) 

L 

24 

2 
O 

2 

30 

30 

IO 

40 
70 


5-5 
SI. 
7 
10 


25 

Note. — The  kind  of  rock  designated  by  the  abbreviations  is  as  follows:  Sp., 
soapstone;  Sd.,  sandstone;  Lm.,  limestone;  Gr.,  granite;  Py.,  quartz  porphyry 
(soft  in  column  J;  hard  in  K) ;  SI.,  slate.  Column  J  applies  to  Rand  drills 
using  chisel  bits;  column  K  to  Leyner- Water  drills  using  X  bits  in  a  softer 
rock. 


F 

G 

H 

I 

J 

K 

Drilling  first  2  ft.,  mins  

20 

10 

5 

10 

554 

3 

i-3 

Cranking  out  and  removing  bit,  mins  

2 

3 

ti 

3 

l/2 

i-3 

Cleaning  out   hole,   mins  

2 

3 

0 

3 

O 

0 

Putting  in   new  bit   and   cranking   back, 

mins  

I 

2Y2 

i 

4 

54 

I] 

[/2 

Drilling  second  2  ft.,  mins  

15 

9 

6 

IO 

19 

4; 

Y4 

Drilling  last  2  ft.,  mins  

IS 

9 

8 

10 

.. 

Shifting    machine     on    column,     hole    to 

hole,   mins  

5 

7 

8 

3X 

5 

5 

Shifting  column,  and  setting  up,  mins.  20 

to  60 

25 

25 

18 

3i 

30 

Air  pressure,  Ibs.  per  sq.  in  

75 

75 

80 

IOO 

75 

75 

Diameter  of  drill  cylinder  

3/4 

354 

354 

3/8 

2 

a 

Y-2. 

"          "    starting  bit    

2*4 

2^/2 

254 

2 

iH 

f 

X 

"          "    fiinishing  bit    

2 

\y2 

i*4 

1/4 

I 

i' 

/4 

Depth   of   hole  ,  

8 

12 

12 

6 

4.6 

S 

•5 

Kind  of   rock  

Sp. 

Sd.  L 

m. 

Gr. 

Py. 

Py. 

No.  of  holes  drilled  at  one  column  set  up 

9 

IO 

12 

IO 

7 

8 

Length  of  shift,  hrs  

10 

IO 

10 

8 

8 

8 

Time  lost  at  blasting,  hrs  

i 

1/4 

(?) 

YI 

i  } 

I 

"         "     mucking  and  timbering,  hrs. 

4 

(?) 

(?) 

f      2 

f 

1 

Ft.  drilled  per  shift  

60 

3i 

38 

78 


ROCK  EXCAVATION—  METHODS  AND  COST. 


Results  of  a  Drilling  Contest.  —  The  following  is  an  ab- 
stract from  an  article  in  the  Mining  Reporter,  July  17,  1902, 
reprinted  in  the  Leyner  drill  catalogue.  Eleven  Water-Ley- 
ner  drills  (model  5),  seven  Ingersoll  drills  and  five  Sulli- 
van drills  (all  3-in.)  were  entered  in  a  drilling  contest  at 
Idaho  Springs,  Col.  Each  drill  was  run  by  an  experienced 
driller  and  helper,  the  different  contestants  bringing  their 
own  drills.  A  face,  or  breast,  was  prepared  near  the  New- 
house  Tunnel,  where  the  rock  is  a  "schist  of  more  than 
average  hardness  for  drill  work."  Each  drill  was  to  put 
in  two  Q-ft.  holes,  one  looking  up,  one  down,  the  angle  not 
exceeding  25°  from  the  horizontal.  The  finishing  bit  was 
\y%  ins.  diam.  The  air  pressure  was  no  Ibs.  I  have  sum- 
marized the  results  of  this  contest  as  follows  :  Nine  of  the 
Leyner  drills  finished  the  contest,  three  of  the  Ingersoll 
drills  and  two  of  the  Sullivan  drills.  Table  XX.  gives  the 
average  results  of  the  drills  that  finished,  as  well  as  the  best 
results  of  an  individual  drill  of  each  of  the  three  makes. 

TABLE  XX. 

Moving 

Setting  Drilling  isttO2d  Drilling  Tearing  Total 
Up.      ist  Hole.     Hole.    2d  Hole.    Down.  Time. 


H 


^ 


en 

G 

8 

en 

G 

en 

en 

c 

g 

en 

tn 

en 

C 

en 

CJ 

en 

G 

en 

s 

t/3 

§ 

C/5 

3 

3 

w 

3 

S 

C/) 

3 

ell 

4 

IO 

28 

2O 

I 

oo 

23 

40 

3 

IO 

60 

2O 

4 

35 

24 

15 

I 

20 

34 

30 

4 

15 

69 

05 

3 

30 

17 

30 

0 

30 

17 

50 

2 

55 

42 

15 

5 

05 

26 

40 

I 

0 

42 

15 

3 

15 

78 

15 

4 

30 

27 

2O 

I 

25 

35 

50 

4 

30 

73 

35 

5 

0 

23 

O 

0 

30 

22 

o 

3 

IO 

53 

40 

Make  of  Drill. 
Leyner  (average)... 
Ingersoll    (average) 
Sullivan    (average). 

Leyner    (best) 5 

Ingersoll*   (best)... 
Sullivan   (best) 

In  studying  this  table  it  is  well  to  note  that  the  first  hole 
the  up  hole,  and  the  second  hole  was  the  down  hole  in 
all  cases.  It  will  be  noticed  that  the  down  hole  required  much 
longer  to  drill  than  the  up  hole  in  the  cases  of  the  Inger- 


This  drill  was  disqualified  because  the  second  hole  was 


ins.  short. 


THE  COST  OF  MACHINE  DRILLING.  79 

soil  and  the  Sullivan  drills.  The  Leyner  drill,  on  the  con- 
trary, showed  very  little  difference  in  speed  of  drilling  either 
up  or  down  holes ;  the  reason  being,  I  think,  due  to  the  fact 
that  the  water  (under  pressure)  that  is  used  with  the  Ley- 
ner drift  keeps  the  bottom  of  the  hole  clean  in  all  cases  (up 
or  down  holes),  leaving  no  cushion  of  sludge  for  the  bit  to 
strike  upon.  The  Ingersoll  and  the  Sullivan  drills  worked 
to  better  advantage  in  the  up,  or  dry  holes,  than  in  the  down, 
or  wet  holes;  because  the  water  used  in  the  wet  holes  was 
not  forced  in  through  a  pipe,  but  merely  thrown  into  the 
hole  with  a  tin  cup  (as  is  the  ordinary  method  of  "tending 
chuck"),  and  in  a  rock  that  makes  sludge  rapidly,  as  many 
schists  do,  the  sludge  accumulates  under  the  bit  and  cushions 
its  blow.  In  an  up  (dry)  hole,  however,  the  chips  and  dust 
roll  out  of  the  hole  as  fast  as  formed,  so  that  much  better 
speed  is  possible  in  a  rock  that  cuts  rapidly,  as  this  particu- 
lar "schist"  evidently  does.  The  Leyner  drill  is  an  excel- 
lent drill  in  soft  rocks,  and  drills  well  also  in  hard  rocks, 
but  with  a  greater  air  consumption  than  any  other  make  of 
drill,  as  is  shown  on  page  55. 

Rule  for  Estimating  Feet  Drilled  per  Shift. — We  are  now 
possessed  of  sufficient  data  to  enable  us  to  formulate  a  rule 
whereby  the  number  of  feet  drilled  per  shift,  under  given 
conditions,  may  be  predicted.  I  will  not  go  into  the  method 
that  I  used  in  deducing  the  following  rule,  which  is  strictly 
correct,  for  the  method  is  one  of  simple  arithmetic.  The 
rule  is : 

To  find  the  number  of  feet  of  hole  drilled  per  shift  divide 
the  total  number  of  working  minutes  in  the  shift  by  the 
sum  of  the  following  quantities:  The  number  of  minutes 
of  actual  drilling  required  to  drill  one  foot  of  hole,  plus  the 
average  number  of  minutes  required  to  change  bits  divided 
by  the  length  of  the  feed  screw  in  feet,  plus  the  average 
number  of  minutes  required  to  shift  the  machine  from  hole 
to  hole  divided  by  the  depth  of  the  hole  in  feet. 

Suppose,  for  example,  the  shift  is   10  hrs.  long,  that  is 


8o          ROCK  EXCAVATION— METHODS  AND  COST. 

600  mins. ;  that  it  requires  5  mins.  to  drill  i  ft.  of  the  rock ; 
that  it  requires  4  mins.  to  change  bits  and  clean  hole;  that 
the  feed  screw  is  2  ft.  long;  that  the  machine  can  be  shifted 
from  hole  to  hole  in  16  mins. ;  and  that  each  hole  is  8  ft. 
deep.  Then  according  to  the  rule  we  have:  The  number 
of  feet  of  hole  per  shift  is  600  -f-  5  +  f  +  V~>  which  is 
equivalent  to  600  -f-  9,  or  66  2-3  ft.  drilled  per  lo-hr.  shift. 

For  those  who  can  use  simple  algebraic  formulas  the 
above  rule  is  much  more  compactly  expressed  in  the  follow- 
ing formula: 

S 


N  = 


N  =  number  of  feet  drilled  per  shift. 
S  =  length  of  working  time  of  shift  in  minutes  =  600 
for  a  lo-hr.  shift  when  no  time  is  lost  by  blasts,  break- 
downs, etc. 

r  =  number  of  minutes  of  actual  drilling  required  to  drill 
i  ft.  of  the  rock. 

m  =  number  of  minutes  required  to  crank  up,  change 
drills,  pump  out  hole  and  crank  down. 

m  =  3  to  4  mins.  ordinarily. 

f  =  length  of  feed  screw,  in  ft.,  ranging  from  ij^  ft-  m 
"baby"  drills  to  2^  ft.  in  largest  drills,  but  ordinarily  2  ft. 
fi  =  number  of  minutes  required  to  shift  machine  from 
one  hole  to  the  next,  including  the  time  of  chipping  and 
starting  the  new  hole,  but  not  including  the  time  of  crank- 
ing up  and  cranking  down. 

$         yS  =  5  mins.  for  very  rapid  shifting  of  a  tripod  ma- 
chine on  level  rock. 
5         JS  —  12  mins.  for  moderate  speed  of  shifting  a  tripod 

machine  on  level  rock. 

S        j&  —  20  mins.  for  very  deliberate  shifting  of  tripod  ma- 
chine on  level  rock. 

,5         $  =  30  to  40  mins.  for  difficult  set  up  of  tripod  in  ir- 
regular rock  surface. 


THE   COST   OF  MACHINE  DRILLING.  81 

^  /gf  —  25  mins.  divided  by  the  number  of  holes  drilled 
from  one  column  set  up  (when  columns  are  used)  plus  2 
mins. 

D  =  depth  of  hole  in  ft. 

Even  a  casual  study  of  the  foregoing  formula,  or  rule, 
must  impress  the  practical  man  with  the  importance  of  the 
lost  time  elements  in  machine  drilling;  consequently  of  the 
value  of  timing  the  operations  of  changing  bits  and  moving 
machines  when  the  men  do  not  know  that  they  are  being 
timed.  Another  feature  that  stands  out  strikingly  is  the 
reduced  output  of  a  drill  working  in  a  shallow  hole.  Let 
the  reader  solve  a  few  problems,  assuming  first  an  average 
depth  of  hole  of  16  ft.  and  finally  an  average  depth  of  only 
2  ft.  (such  as  occurs  often  in  the  skimming  work  in  road 
building),  and  he  will  never  make  the  blunder  of  the  con- 
tractor who  bid  the  same  price  for  rock  excavation  on  the 
2-ft  deepening  of  the  Erie  Canal  as  had  been  bid  for  the 
36- ft.  excavation  on  the  Chicago  Canal. 

The  best  way  of  showing  the  remarkable  effect  that  the 
depth  of  hole  has  upon  the  number  of  feet  drilled,  when 
the  drill  is  mounted  upon  a  tripod,  is  to  apply  the  rule  given 
on  page  79.  If  we  assume  that  the  shift  is  10  hrs.  long;  that 
the  rate  of  drilling  is  I  ft.  in  5  mins. ;  that  it  takes  4  mins. 
to  change  bits  and  pump  out  the  hole  at  each  change  of 
bits;  that  the  feed  screw  is  2  ft.  long;  and  that  it  takes  15 
mins.  to  shift  from  one  hole  to  the  next;  by  applying  the 
rule  we  obtain  the  following  results: 

Depth  of  hole,  ft I       2       3       5      10     15     20 

Feet  drilled  in  10  hrs.      27     41     50     60     70     75     80 

When  drillers  are  lazy  they  may  readily  consume  8  mins. 

in  changing  bits  and  pumping  out  the  hole  each  time.  With 

all  conditions  the  same  as  before,  excepting  that  8  mins.  are 

consumed  in  changing  bits,  we  have  the  following  results: 

Depth  of  hole,  ft 12       3       5      10     15     20 

Feet  drilled  in  10  hrs.      25      36    43     50     57     60     62 


82          ROCK  EXCAVATION— METHODS  AND  COST. 

It  will  be  seen  that  in  deep  hole  drilling  20  per  cent,  de- 
creased efficiency  results  from  just  a  little  laziness  in  chang- 
ing bits,  under  the  conditions  assumed;  and  in  softer  rocks 
the  percentage  of  decreased  efficiency  is  much  greater. 
Where  the  holes  are  shallow  the  time  involved  in  shifting 
from  one  hole  to  the  next  becomes  an  important  factor.  As- 
suming that  the  conditions  are  the  same  as  in  the  first  in- 
stance, except  that  30  mins.  are  consumed  in  shifting  from 
one  hole  to  the  next;  then  we  have  the  following  results : 

Depth  of  hole,  ft i       2       3       5      10     15     20 

Feet  drilled  in  10  hrs.  16  27  35  46  60  67  70 
In  similar  manner  I  might  tabulate  other  results  derived 
by  varying  the  different  time  elements  in  drilling;  but 
enough  has  been  given  to  show  the  supreme  practical  im- 
portance of  studying  these  details,  which  so  many  practi- 
cal men  have  apparently  ignored.  I  leave  it  to  the  reader 
to  apply  the  rule,  or  formula,  to  other  cases,  for  the  results 
of  such  personal  application  of  the  rule  will  stick  in  the 
memory  and  be  of  more  real  value  than  much  reading  of 
tabulated  information. 

Rates  of  Drilling  in  Different  Rocks. — Unfortunately  no 
published  record  exists  showing  rates  of  drilling  in  different 
kinds  of  rock  with  given  air  or  steam  pressures  and  given 
sizes  of  drill  bits.  Such  scattering  records  as  are  to  be 
found  merely  give  the  feet  of  hole  drilled  per  shift.  Tables 
XVIII.  and  XIX.  give  a  fair  idea  of  the  speed  of  actual 
drilling,  and  from  them  together  with  other  data  obtained, 
by  observation  I  have  compiled  the  following  table  for  drill- 
ing with  3j/6-in.  machines  using  air  or  steam  at  70  Ibs.  pres- 
sure, starting  bit  about  2^  ins.  and  finishing  bit  about  il/2 
ins.: 

Time  to  drill  I  ft. 

Soft  sandstones,  limestones,  etc 3  mins. 

Medium,  ditto    4      " 

Hard  granites,  hard  sandstones,  etc 5      " 

Very  hard  traps,  granites,  etc 6  to  8 

Soft  rocks  that  sludge  rapidly 8  to  10    " 


THE   COST   OF   MACHINE   DRILLING.  83 

The  foregoing  data  apply  only  to  drilling  where  no  time 
is  lost  by  the  sticking  of  the  bit  in  the  hole,  and  only  with 
air  pressure  and  bits  approximately  as  above  given.  The 
reader  should  now  read  again  the  text  on  pages  52  to  55, 
noting  especially  the  falling  off  in  the  rate  of  drilling  ac- 
companying decreased  air  pressure.  He  should  also  study 
the  table  on  page  54,  relating  to  the  effect  of  size  of  bit 
upon  speed  of  drilling,  remembering  that  all  the  tests  there 
recorded  relate  only  to  shallow  holes.  As  holes  grow  deeper 
the  bit  grows  smaller,  but  at  the  same  time  the  drill  steel 
grows  heavier,  in  consequence  of  which  the  last  2  ft.  of  a 
deep  hole,  with  a  bit  only  il/2  ins.  in  diam.,  are  ordinarily 
drilled  no  faster  than  the  first  2  ft.  with  a  much  larger  bit. 
With  a  powerful  drill  and  a  water  jet  it  is  quite  possible  that 
the  last  2  ft.  might  be  drilled  faster  than  the  first  2  ft. 

Note  especially  that  if  a  water  jet  is  not  used,  drilling 
may  actually  be  slower  in  a  soft,  friable  rock,  like  shale, 
than  in  the  toughest  trap.  This  fact  is  well  brought  out  in 
Table  XIX.,  column  "K,"  where  the  drilling  of  the  second  2 
ft.  of  hole  consumed  19  mins. !  Yet  this  material  was  a  soft 
porphyry  that  with  a  water  jet  was  penetrated  at  the  rate 
of  2  ft.  in  less  than  5  mins.,  as  shown  in  column  "K."  While 
the  Leyner- Water  drill  is  an  excellent  machine  for  drilling 
shallow  holes  in  rock  that  makes  sludge  rapidly,  its  excel- 
lence is  due  primarily  to  the  use  of  water  under  pressure. 
In  drilling  granite  its  speed  is  no  greater  than  that  of  the 
best  types  of  the  ordinary  percussion  rock  drill. 

Reverting  to  the  subject  of  air  or  steam  pressure  as  af- 
fecting  the  speed  of  drilling,  it  is  not  always  easy  to  gage 
the  pressure  at  the  drill ;  but  I  have  found  it  a  simple  matter 
to  estimate  the  pressure  with  considerable  accuracy  by 
noting  the  number  of  blows  per  minute  struck  by  the  drill. 
Using  drill-steel  of  given  weight,  first  test  the  drill  for  speed 
at  a  point  so  near  the  compressor  or  boiler  that  little  or  no 
loss  of  pressure  can  occur  in  the  pipe  line.  Vary  the  pres- 
sure from,  say,  80  down  to  40  Ibs.  in  making  the  test  of 


84         ROCK  EXCAVATION— METHODS  AND  COST. 

the  number  of  blows  struck  per  minute,  and  thereafter  your 
pencil  and  your  watch  will  be  a  good  enough  pressure  gage. 
The  number  of  blows  can  be  counted  by  keeping  time  with 
a  pencil.  The  pencil,  in  the  hands  of  the  observer,  is  made 
to  strike  a  sheet  of  paper  every  time  the  drill  strikes  the 
rock.  Then  at  the  end  of  a  definite  number  of  seconds,  say 
15  sees.,  the  number  of  marks  of  the  pencil  point  upon  the 
paper  are  counted,  and  the  number  of  blows  per  minute  are 
computed. 

Once  it  has  been  ascertained  how  many  blows  a  given 
size  drill  strikes  per  minute  when  working  at  full  stroke, 
under  varying  gage  pressures,  the  only  gage  needed  is  the 
pencil,  and  a  watch ;  for  the  pressure  can  be  roughly  ascer- 
tained by  determining  the  number  of  blows  struck  per 
minute.  This  I  have  found  to  be  an  exceedingly  useful 
means  of  ascertaining  whether  or  not  too  many  drills  are 
drawing  power  from  a  given  pipe  line.  If  a  given  steam 
boiler  or  compressor  is  designed  to  supply  15  drills,  and  if 
it  is  afterward  loaded  up  with  20  drills,  the  pressure  at  each 
drill  will  be  reduced,  resulting  in  a  very  decided  falling  off 
in  the  number  of  feet  of  hole  put  down  daily  by  each  drill. 

Average  Footage  Drilled  per  Shift, — In  subsequent  chap- 
ters many  records  of  actual  work  are  given,  but  that  the 
inexperienced  reader  may  have  a  good  general  conception 
of  what  constitutes  a  day's  work  under  ordinary  conditions 
the  following  summary  may  be  of  benefit :  In  drilling  ver- 
tical holes,  with  the  drill  on  a  tripod,  the  holes  being  from  10 
to  20  ft.  deep,  shift  10  hrs.  long,  I  have  found  that  in  the 
hard  "granite"  of  the  Adirondack  Mts.,  N.  Y.,  48  ft.  is  a 
fair  lo-hr.  day's  work.  In  the  granites  of  Maine  and  Massa- 
chusetts 45  to  50  ft.  is  a  day's  work.  In  New  York  City, 
where  the  rock  is  mica  schist,  deep  holes  are  drilled  at  the 
rate  of  60  to  70  ft.  per  lo-hr.  shift  by  men  willing  to  work, 
but  40  to  50  is  nearer  the  average  of  union  drillers.  In  the 
very  hard  trap  rock  of  the  Hudson  River  40  ft.  is  considered 
a  fair  day's  work.  In  the  soft  red  sandstone  of  northern 


THE   COST  OF  MACHINE   DRILLING.  85 

New  Jersey  90  ft.  are  readily  drilled  per  day  wherever  the 
rock  &  not  so  seamy  as  to  cause  lost  time  by  the  sticking  of 
the  bit;  in  fact,  I  have  records  showing  no  ft.  per  lo-hr. 
shift  in  this  rock.  In  the  hard  limestone  near  Rochester 
my  records  show  about  70  ft.  per  lo-hr.  shift.  In  the  lime- 
stone on  the  Chicago  Drainage  Canal  70  to  80  ft.  was  a  10- 
hr.  day's  work.  In  the  hard  syenite  of  Douglass  Island,  in 
open  pit  work,  and  where  it  is  difficult  to  make  set-ups,  36 
ft.  is  now  the  average  per  lo-hr.  day.  In  the  limestone  near 
Windmill  Pt,  Ontario,  3^-in.  drills  average  75  ft.  a  day 
(holes  18  ft.  deep)  ;  2^-in.  drills,  60  ft.  a  day,  and  "baby" 
drills,  37  ft.  a  day. 

The  foregoing  examples  all  apply  to  comparatively  deep 
vertical  holes,  in  open  excavation.  In  tunnel  work  there  is 
no  reason  why  a  drill  should  not  do  about  the  same  work 
per  shift,  were  there  no  delays  in  timbering,  mucking,  wait- 
ing for  gases  to  clear,  etc.  Such  delays,  however,  often  re- 
duce the  drill  footage  very  much,  as  will  be  seen  in  subse- 
quent chapters. 

Cost  of  Sharpening  Bits. — In  the  South  African  gold 
mines  each  machine  averages  20  drills  per  shift,  and  taking 
the  average  weight  at  15  Ibs.  per  drill,  it  is  evident  that  600 
Ibs.  of  drills  must  be  carried  to  and  from  the  shop  for  each 
machine  per  shift.  Where  30  drills  are  at  work  this  means 
the  transportation  of  9  tons  of  drills  each  shift — an  item  in 
itself  worthy  of  consideration. 

One  blacksmith  (with  a  helper)  will  sharpen  about  140 
bits  a  day,  and  under  ordinary  conditions  will  keep  5  to  7 
drills  supplied  with  sharp  bits.  In  average  rock  a  bit  must 
be  sharpened  for  every  2  ft.  of  hole ;  in  very  soft  rock  a  bit 
for  every  4  ft.,  and  in  very  hard  rock  a  bit  for  every  1^/2  ft. 
of  hole. 

Sharpening  140  bits  by  hand  costs  $3  for  blacksmith's 
wages,  $2  for  helper  and  60  cts.  for  charcoal,  or  4  cts.  per 
bit. 

Mr.  Edward  D.  Self,  Manager  and  Engineer  San  Carlos 


86          ROCK  EXCAVATION— METHODS  AND  COST. 

Copper  Co.,  San  Jose,  Mexico,  writes  me  that  185,828  hand 
drills  were  sharpened  in  drilling  about  65,000  ft.  of  hole,  at 
a  cost  of  2  cts.  per  bit  (Mexican  currency)  ;  and  that  10,- 
ooo  machine  drill  bits  were  sharpened  by  hand  at  a  cost  of  3 
cts.  each  (Mexican  currency). 

For  sharpening  large  numbers  of  bits  daily,  drill  sharpen- 
ing machines  are  much  cheaper  than  hand  sharpening,  as 
shown  on  page  30. 

Cost  of  Drill  Repairs. — Mr.  Thomas  Dennis,  agent  of  the 
Adventure  Consolidated  Copper  Co.,  Hancock,  Mich.,  has 
kindly  furnished  the  following  data  of  the  average  monthly 
cost  of  keeping  a  drill  in  repair: 

Supplies  for  repairs   $1.31 

Machinist  labor   8.45 

Blacksmith  labor   .  1.60 


Total  repair  charge  per  month $11-36 

The  number  of  drills  in  the  shop  at  any  one  time  is  about 
15  per  cent,  of  the  total  number.  This  low  cost  is  based 
upon  work  where  a  large  number  of  drills  are  used  and  well 
handled  by  the  users. 

I  am  indebted  to  Mr.  Josiah  Bond,  mining  engineer,  for 
i4^  the  statement  that  the  cost  of  repairs  averages  50  cts.  per 
-^  drill  per  shift  in  mines  where  a  few  drills  are  operated  awl 
renewal  parts  purchased  from  the  manufacturers.  In  open 
cut  work  my  experience  is  that  75  cts.  per  drill  per  shift  is 
a  fair  allowance  for  renewals  and  repairs.  In  the  gold  mines 
of  South  Africa,  where  each  drill  works  two  shifts  per  day, 
the  cost  of  drill  repairs  is  $300  per  drill  per  year;  while  the 
first  cost  of  a  3^4-in.  drill  with  bar  is  $185,  according  to  a 
recent  report  of  the  Government  Mine  Inspector. 

Plant  Rental. — This  term  is  a  convenient  one  to  use  in- 
stead of  "interest  and  depreciation,"  moreover  "plant  rental" 
is  a  term  that  clearly  excludes  the  cost  of  current  repairs.  It 
is  exceedingly  difficult  to  nanie  any  definite  percentage  to  be 


THE   COST   OF  MACHINE   DRILLING.  87 

allowed  for  rental  of  a  drilling  plant,  because  the  term  of 
years  during  which  the  plant  will  be  operated  by  the  pur- 
chaser is  usually  a  matter  of  guess  work.  Little  or  nothing 
can  be  borrowed  from  banks  upon  a  drilling  plant  as  the 
only  collateral ;  hence  the  owner  of  a  plant  is  not  justified 
in  charging  only  the  legal  rate  of  interest  for  rental  even 
if  the  plant  were  to  have  an  everlasting  life.  The  owner 
should  charge  for  interest  on  the  plant  all  that  he  could  earn 
in  the  way  of  profits  if  he  had  the  plant  money  invested 
otherwise  in  his  business.  The  life  of  a  plant  is  only  a  few 
years  at  best,  since  improvements  in  machinery  are  con- 
stantly taking  place.  Moreover  "dull  times"  put  scores  of 
plants  upon  the  idle  list  for  indefinite  periods  of  time.  In 
view  of  these  facts  it  is  good  business  policy  to  charge  the 
whole  cost  of  a  drilling  plant  up  against  the  contract  job  for 
which  it  is  purchased,  if  the  job  is  a  large  one.  For  small 
mines  and  small  jobs  generally,  it  is  wise  to  charge  up  20 
to  40  per  cent,  of  the  first  cost  of  the  plant  for  annual 
"rental"  or  "sinking  fund."  Divide  this  annual  "rental"  by 
the  total  number  of  shifts  that  will  probably  be  worked  dur- 
ing the  year,  to  arrive  at  a  probable  rental  cost  per  shift; 
and  in  estimating  the  probable  working  days  in  the  year 
make  liberal  allowance  for  strikes,  bad  weather  and  sundry 
delays.  In  the  estimates  of  cost  that  follow  I  purposely 
omit  an  allowance  for  "plant  rental,"  because  each  case  must 
be  treated  as  a  problem  in  itself ;  nevertheless,  "plant  rental" 
is  often  a  very  important  item  and  one  that  is  not  infre- 
quently forgotten  entirely  in  making  estimates  of  cost. 

Cost  of  Installing  a  Compressor  Plant. — The  following  is 
an  itemized  account  of  the  cost  of  installing  a  small  com- 
pressor plant.  The  compressor  was  a  Rand,  Class  C,  24  x 
3O-in.,  that  cost  $4,000.  The  boiler  was  a  second-hand  150 
H.-P.  locomotive  boiler  that  cost  $1,000.  This  plant  was 
capable  of  furnishing  1,300  cu.  ft.  of  free  air  per  min.  at  80 


88          ROCK  EXCAVATION— METHODS  AND  COST. 

Ibs.  pressure,  or  enough  to  run  10  or  12  drills.     Cost  of  in- 
stalling boiler: 

22  days    laborers,  at  $1.50   $33 

23  "      engineers,  at  $3 69 

13  mechanics,  at  $4   52. 

13      "  "  help,  at  $2   26 

i      "      bricklayer,   at  $4    4 


Total    $184 

Cost  of  installing  compressor : 

120  days   laborers,  at  $1.50 $180 

4      "      engineers,  at  $3    12 

22      "      mechanics,   at  $4    88 

80      "              "          help,  at  $2 1 60 

50      "     carpenters,  at  $3   150 

3      "      bricklayers,  at  $4   12 

6      "      teams,  at  $4 24 

8      "      foremen,  at  $3    24 

Total    $650 

Cost  of  materials: 

I5M  lumber  for  housing  compressor,  at  $25.  .$375 

1,400  sq.  ft.  tar  paper  (i  layer)   21 

32  cu.  yds.  concrete,  at  $4 128 

5M  brick,  at  $7 35 

6  bbls.  cement,  at  $2  12 

Sand I 

Total     $572 

Cost  of  a  Large  Compressor  Plant. — The  following  is  the 
estimated  cost  of  a  compressed  air  plant  for  a  western  mine, 
the  compressor  being  designed  to  carry  20  drills  (3^-in. 
size)  : 

4  high  pressure  boilers  (66-in.  x  16  ft) $6,000 

Housing  and  installing  boilers 2,000 


THE   COST   OF  MACHINE   DRILLING.  89 

Duplex   compound  air  compressor 16,000 

Housing  and  installing  compressor 2,000 

Pipe,  1,000  ft.  of  6-in.,  and  1,500  ft.  of  I  in..    1,200 
Machine  shop  and  tools  800 

Total    $28,000 

It  is  usually  safe  to  estimate  on  a  basis  of  $130  to  $150 
per  drill  for  the  cost  of  a  large  and  efficient  compressor  plant 
and  pipe  line,  to  which  must  be  added  the  cost  of  the  drill 
itself,  which  is  about  $250  for  a  3^-in.  drill  mounted. 

Cost  of  Operating  Drills. — When  operating  a  single 
(3/4"m-)  drill  supplied  by  steam  from  a  small  portable 
boiler,  I  find  the  cost  is  usually  as  follows  for  a  lo-hr.  shift : 

i  drill  runner $3*oo 

i  drill  helper   1.75 

I   fireman    2.00 

660  Ibs.  of  coal  (0.3  ton  at  $3) 90 

Water  if  hauled,  say 75 

Hauling  and  sharpening  30  bits   (incl.  new 

steel)  at  4  cts 1.20 

Repairs  to  drill  and  hose  renewals 75 


Total  per  10  hrs $10.35 

The  foregoing  is  merely  an  example,  based,  however, 
upon  several  different  jobs ;  but  in  each  case  the  accessibility 
of  a  blacksmith,  the  nearness  to  water,  the  price  of  coal  de- 
livered at  the  boiler,  etc.,  must  be  determined  before  an  ac- 
curate estimate  can  be  made.  If  4  drills,  for  example,  are 
to  be  operated  from  the  same  boiler,  the  fuel  bill  will  be 
somewhat  reduced  even  if  the  pipes  are  not  covered  with 
asbestos,  and  of  course  the  wages  of  the  fireman  will  be  dis- 
tributed over  4  drills.  It  will  then  pay  to  have  a  black- 
smith at  hand.  If  10  or  more  drills  are  run  by  steam  from 
a  central  boiler,  and  if  the  main  pipes  are  lagged,  the  fuel 
should  not  much  exceed  300  Ibs.  per  drill  per  lo-hr.  shift. 
By  the  rules  previously  given  a  fairly  close  estimate  can  be 


QO"        ROCK  EXCAVATION— METHODS  AND  COST. 

made  of  the  number  of  feet  of  hole  that  each  drill  should 
average.  If  60  ft.,  for  example,  is  to  be  a  fair  day's  work  in 
limestone  or  sandstone,  we  have  $10.35  -^  60  =  17  cts.  per 
ft.  as  the  cost,  exclusive  of  superintendence,  plant  installa- 
tion and  plant  rental. 

If  a  central  compressor  or  steam  plant  supplies  power 
for,  say,  15  drills,  we  may  estimate  the  cost  of  operating 
each  drill  as  follows : 

i  drill  runner $3.00 

i  drill  helper   1.75 

1-15  fireman  at  $2.25 15 

1-15  compressor  man  at  $3 20 

300  Ibs.  coal  (water  nominal)  at  $3  ton 45 

Sharpening  bits,  30  at  3  cts 90 

Repairs  to  drill,  hose,  etc 75 


Total  for  60  ft.  of  hole  at  12  cts $7.20 

If  the  cost  of  each  drill  and  1-15  part  of  the  compressor 
plant  is  $350,  and  30  per  cent,  of  this  is  assumed  as  a  fair 
allowance  for  annual  plant  rental,  we  have  $105  to  charge 
up  against  each  drill  for  "rental,"  or  about  50  cts.  per  shift 
if  200  shifts  are  worked  each  year,  or  about  i  ct.  per  ft.  of 
hole  drilled. 

Cost  of  Drilling  Blast  Holes  with  a  Well  Driller.— In  En- 
gineering News  I  first  described  the  use  of  well  drillers  on 
the  Pennsylvania  Railroad  work  for  drilling  blasting  holes. 
The  well  drillers  used  were  the  ordinary  type  of  portable 
driller,  consisting  of  a  wagon  on  which  is  mounted  a  4  to 
8  H.-P.  engine  that  drives  a  walking  beam;  the  walking 
beam  raises  and  lowers  a  rope,  to  which  is  fastened  the 
churn  bit  and  rods  that  form  the  "business  end"  of  the 
driller.  A  5^-in.  bit  was  used  in  this  work,  and  even  witn 
this  large  bit  each  drill  averaged  three  20- ft.  holes,  or  60  ft., 
drilled  in  shale  per  lo-hr.  shift.  In  limestone,  however,  and 
in  hard  sandstone  not  more  than  10  ft.  of  hole  were  drilled 
per  shift.  In  describing  the  use  of  the  well  driller  for  this 
purpose  I  suggested  that  if  the  bits  were  reduced  to  about 


THE   COST   OF  MACHINE   DRILLING. 


9^^ki£P8Nl! 


3  ins.  in  diam.,  and  if  the  drill  rods  were  suitably  weighted, 
much  better  progress  would  be  made  in  hard  rock.  Shortly 
afterward  the  Cyclone  Drilling  Machine  Co.,  of  Orrville, 
Ohio,  put  upon  the  market  a  driller  especially  designed  for 
contractors  doing  railroad  work.  The  Cyclone  driller  has 
a  5  H.-P.  engine,  uses  a  3~in.  bit,  has  drill  rods  that  screw 
together  and  a  suitable  weight  to  give  power  to  the  blow, 
and  the  whole  outfit  on  trucks  weighs  only  5,000  Ibs.  Fig. 
6  shows  one  of  these  drillers  at  work  on  the  Wabash  Rail- 


Fig.  6. 

road.  For  this  type  of  driller  I  predict  an  increasingly 
large  field,  for  the  following  reasons :  ( i )  A  drill  will  not 
stick  in  the  hole,  because  of  the  powerful  direct  pull  of  the 
rope  that  operates  the  drill  rods;  (2)  there  is  no  limit  to 
the  depth  of  the  hole,  and  the  deeper  it  is  (up  to  any  limits 
possible  in  blasting)  the  better  the  drill  works,  due  to  the 
increased  weight  of  the  rods;  (3)  this  type  of  drill  con- 
sumes less  fuel  than  the  ordinary  steam  drill ;  (4)  the  weight 
of  bits  to  be  carried  back  and  forth  from  blacksmith  shop 


92          ROCK  EXCAVATION— METHODS  AND  COST. 

is  much  less  than  for  the  ordinary  machine  drills;  (5)  the 
driller  will  drill  through  the  earth  overlying  the  rock,  so 
that  no  stripping  is  necessary.  Mr.  W.  M.  Douglass,  of 
Douglass  Bros.,  contractors,  was  kind  enough  to  keep 
records  for  me  showing  the  cost  of  operating  one  of  these 
cyclone  drillers  compared  with  a  Rand  drill.  The  following 
are  the  data: 

The  holes  were  drilled  with  bits  to  give  3  ins.  diam.  at  the 
bottom  of  the  hole.  Holes  were  24  ft.  deep  in  solid  brown 
sandstone  in  eastern  Ohio.  In  14  days,  of  10  hrs.  each,  the 
driller  put  down  692  ft.,  or  practically  50  ft.  per  day.  The 
daily  cost  of  operating  was  as  follows : 

Drill    runner    $3.00 

Drill  helper  and  fireman 2.00 

Pumping  water 60 

6  bu.  (480  Ibs.)  coal  at  10  cts 60 


Total  for  50  ft.  of  hole  $6.20 

This  gives  a  cost  of  12^2  cts.  per  ft.  of  hole,  not  includ- 
ing interest  and  depreciation  and  bit  sharpening.  The  best 
day's  work  in  the  brown  sandstone,  using  all  the  weights, 
was  53  ft.,  but  in  blue  sandstone,  which  was  softer,  60  ft. 
were  drilled  per  day  using  light  weights. 

In  the  same  brown  sandstone  cut  an  8-day  test  was  made 
with  a  3/4~in.  Rand  drill  for  comparison.  The  holes  were 
20  ft.  deep,  1^4  ms.  diam.  at  the  bottom  (as  against  3  ins. 
with  the  well  driller),  and  28  holes  were  drilled  in  the  8 
days,  making  70  ft.  the  average  day's  work.  A  10  H.-P. 
boiler  furnished  steam.  The  daily  cost  of  operating  the 
Rand  drill  was : 

Drill  runner   $3-OO 

Drill   helper    1.50 

Fireman 2.00 

Water    75 

10  bu.  (800  Ibs.)  coal  at  10  cts i.oo 

Total  for  70  ft.  of  hole $8.25 


THE   COST   OF   MACHINE   DRILLING.  93 

This  was  equivalent  to  n.8  cts.  per  ft.  of  hole,  not  in 
eluding  interest  and  depreciation  and  drill  sharpening. 

It  should  be  observed  that  the  well  driller  holes  were 
deeper  (and  they  could  have  been  still  deeper  without  in- 
creasing the  cost  per  foot)  as  well  as  larger  in  diameter 
than  the  Rand  drill  holes.  The  greater  diameter  saved  a 
considerable  amount  of  dynamite  in  springing  the  holes, 
since  each  well  driller  hole  was  sprung  three  times,  as  com- 
pared with  four  or  five  times  for  the  Rand  drill  holes,  in 
order  to  make  a  chamber  large  enough  to  hold  the  black 
powder.  Mr.  Douglass  has  made  some  interesting  tests 
on  the  use  of  black  powder  and  dynamite  in  alternate  rows 
of  holes,  for  which  see  page  149. 

I  would  suggest  a  further  improvement  in  this  type  of 
driller,  namely,  the  use  of  a  gasoline  engine  instead  of  a 
steam  engine.  Such  a  change  would  do  away  with  the  cost 
of  water  for  the  boiler.  It  would  also  make  it  unnecessary 
to  have  a  fireman. 

Cost  of  Drilling  with  Electric  Drills. — Upon  this  subject 
there  is  practicality  nothing  in  print.  I  am  indebted  to  Mr. 
J.  B.  Hobson,  Manager  Caribou  Hydraulic  Co.,  Bullion, 
B.  C,  for  the  following  cost  data:  Four  Gardner  Electric 
Drill  Co.'s  No.  15  drills,  with  2  H.-P.  motors,  and  one  "B" 
drill  with  a  i^  H.-P.  motor,  have  been  used  for  two  years 
by  Mr.  Hobson  with  excellent  results.  Each  of  the  larger 
drills  has  averaged  13  holes,  8  ft.  deep,  in  firm  augite  diorite 
and  porphyrite,  per  lo-hr.  shift.  The  starting  bit  is  2.y2  ins. 
and  the  finishing  bit  il/2  ins.  in  diameter.  The  cost,  per  10- 
hr.  shift,  of  operating  three  drills  has  been  as  follows : 

i  cord  of  wood  $2.25 

I  electrical  engineer   4.00 

3  drillers,  at  $4 12.00 

3  helpers,  at  $2 6.00 

i  blacksmith   4.00 

i  blacksmith's  helper   2.00 


94          ROCK  EXCAVATION— METHODS  AND  COST. 

3  bu.  charcoal $0.75 

Oil    55 

Total  for  3  drills,  312  ft.  drilled $31-55 

The  cost  of  drilling,  including  sharpening,  but  excluding 
interest  and  depreciation,  was  10  cts.  per  foot  of  hole.  See 
page  20  for  cost  of  hand  drilling  in  the  same  rock. 

In  Trans.  Am.  Inst.  Min.  Eng.,  1903,  Mr.  Frank  E.  Shep- 
ard  describes  the  box  electric  drill  which  is  manufactured 
by  the  Denver  Engineering  Works,  Denver,  Colo.  The  drill 
steel  is  not  churned  but  is  struck  by  the  piston,  resembling 
the  Leyner  drill  in  this  respect.  Water  is  forced  down 
through  a  pipe  which  slips  over  the  drill  steel,  and  the  sludge 
is  washed  out  of  the  hole.  In  drilling  a  block  of  granite 
from  Platte  Canyon,  Colo.,  an  electric  current  of  n  am- 
peres at  no  volts  was  used,  which  is  equivalent  to  1.62 
H.  P.  A  hole  2)4  ins.  in  diameter  was  drilled,  the  first  16 
ins.  being  drilled  in  7  mins. ;  then  I  min.  was  consumed  in 
changing  bits.  The  next  14  ins.  were  drilled  in  5  mins., 
and  i  min.  more  was  consumed  in  changing  bits.  The  last 
3^2  ins.  were  drilled  in  £4  min.  The  rate  for  the  full  33)^ 
ins.  was  2.23  ins.  per  minute.  In  tunnel  work  in  Boulder 
County,  Colo.,  one  machine  drilled  12)^  ft.  of  holes  (number 
of  holes  not  given),  2)4  ms-  diam.,  in  hard  granite  in  2 
hrs.  Three  tunnel  holes,  each  5  ft.  deep,  were  drilled  in 
2)4  hrs.  In  shaft  sinking  at  the  Ophir  Mine,  Anaconda, 
Colo.,  five  4-ft.  holes  were  drilled  in  3)^  hrs.  •  In  the  tunnel 
of  Imogen  Basin  Gold  Mines  Co.,  Ouray,  Colo.,  four  holes 
5  ft.  deep,  were  drilled  in  3  hrs.  in  soft  rock  with  mud  slips 
running  through  the  seams. 


CHAPTER  VI. 
COST  OF  DIAMOND  DRILLING. 

For  determining  the  nature  of  bridge  foundations  the  char- 
acter of  proposed  canal  or  railway  excavations  and  for  pros- 
pecting for  mineral  deposits,  the  diamond  drill  is  an  invalu- 
able machine.  The  bit  of  a  diamond  drill  consists  of  a  num- 
ber of  diamonds  mounted  on  the  end  of  a  hollow  tube.  This 
bit  is  rotated  by  hand,  steam,  air  or  electric  power,  while  at 
the  same  time  water  is  pumped  down  the  hollow  drill  rods 
and  passes  up  outside  of  the  rods,  carrying  away  the  rock 
dust  made  by  the  grinding  of  the  diamonds  against  the 
rock.  The  bit  cuts  an  annular  channel,  leaving  a  core  of 
rock  inside  the  core  barrel.  When  the  drill  has  penetrated 
the  rock  a  distance  of  6  to  10  ft.,  the  drill  rods  are  raised 
and  the  act  of  raising  them  breaks  off  the  rock  core,  which 
is  brought  to  the  surface  in  the  core  barrel  and  kept  for 
examination. 

The  diamonds  are  preferably  black  diamonds,  known  in 
the  trade  as  "carbons";  but  where  the  rock  is  soft,  white 
diamonds,  known  as  "borts,"  may  be  used.  Sometimes  both 
kinds  are  used  in  one  bit.  A  bit  usually  has  6  to  8  carbons 
weighing  I  to  I  ^2  carats  each.  Small  stones  are  not  econom- 
ical because  after  a  carbon  has  been  worn  down  so  that  it 
weighs  less  than  about  ^2  carat  it  cannot  be  reset.  In  se- 
lecting carbons  reject  those  showing  a  cokey  structure,  also 
those  having  thin,  sharp  edges.  Carbons  having  straight 
edges  with  sides  forming  an  obtuse  angle  of  95°  to  140°  are 
most  durable.  The  cleavage  should  be  tested  with  a  pair  of 
hand  pincers.  Old  stones  that  have  been  used  are  to  be  pre- 
ferred since  a  poor  stone  will  break  in  use,  and  no  test  is  so 
satisfactory  as  the  test  of  usage.  The  carbons  selected  for 
a  bit  should  be  quite  uniform  in  size. 

95 


96          ROCK  EXCAVATION— METHODS  AND  COST. 

When  diamond  drilling  was  first  introduced  into  this  coun- 
try it  was  predicted  that  it  would  be  used  exclusively  for 
drilling  blast  holes,  and  in  fact  diamond  drills  were  used  on 
the  Sutro  tunnel  for  a  while,  and  in  sinking  one  or  two 
shafts  by  the  "long  hole"  method,  which  involved  drilling 
holes  several  hundred  feet  deep,  filling  them  with  sand,  then 
removing  the  sand  for  about  8  ft.,  charging  with  powder, 
firing,  and  so  on.  The  development  of  machine  drills  using 
steel  bits  and  the  steady  rise  in  price  of  carbons  have  to- 
gether shown  these  early  predictions  to  have  been  fathered 
by  hope  rather  than  by  reason. 

The  sizes  of  holes  and  cores  are  as  follows : 

Hole,  diam.  in  ins....     i^  i^4  2  2^        3  9/16 

Core,      "       "    "    ....       15/16      13/16        17/16        2  2ft 

Price  of  Diamonds. — In  1873  the  price  of  carbons  per  carat 
was  $8  to  $12,  whereas  now  the  price  is  about  $50.  I  am  in- 
debted to  the  Standard  Diamond  Drill  Co.,  of  Chicago,  and 
to  the  Yawger-Lexow  Co.,  of  New  York,  for  the  follow- 
ing statements  as  to  the  average  cost  of  carbons  per  carat 
from  1895  to  1903 : 
i§95.  1896.  1897.  1898.  1899.  1900.  1901.  1902. 

$36       $50  $60  $55       $50  $45  $50 

$18.50       $28       $35-50       $35-50       $36       $51.50       $48.50       $47 

It  will  be  noted  that  these  firms  do  not  agree  very  closely 
as  to  prices  prior  to  the  year  1900.  The  American  Diamond 
Rock  Drill  Co.,  of  New  York,  quoted  $52  per  carat  for  best 
selected  carbons  and  $16  per  carat  for  best  selected  borts  in 
November,  1902. 

There  is  no  import  duty  on  carbons  in  the  United  States, 
Canada  01  Mexico. 

Water  Required. — In  boring  a  2-in.  hole  where  the  prog- 
ress is  about  10  ft.  per  lo-hr.  shift,  from  100  to  125  gals,  of 
water  are  required  to  wash  out  the  sludge  formed  in  drill- 
ing, provided  the  water  is  used  but  once.  In  cases  where  the 
water  is  expensive  it  is  customary  to  collect  the  return  water 
in  a  settling  tank  and  use  it  over  and  over;  and,  unless  a 
large  amount  of  water  escapes  through  crevices,  30  or  40 


COST  OF   DIAMOND  DRILLING.  97 

gals,  per  shift  will  be  consumed  by  evaporation  and  leakage. 

Price  of  Diamond  Drills. — A  hand  power  drill  that  can  be 
used  to  bore  a  i^-in.  hole  (giving  a  i5-i6-in.  core)  up  to  a 
depth  of  350  ft. ;  or  a  2^-in.  hole  (giving"  a  2-in.  core)  up 
to  a  depth  of  250  ft.,  will  cost  approximately  $850  f.  o.  b. 
New  York  or  Chicago.  This  includes  300  ft.  of  pipe,  6  car- 
ats of  carbons,  all  tools,  etc.,  necessary.  The  machine  alone 
weighs  330  Ibs.,  and  can  be  divided  into  packages  weighing 
40  Ibs. ;  but  the  whole  outfit  packed  for  shipment  weighs 
2,800  Ibs.  If  it  is  desired  to  run  this  drill  by  horse  power, 
$60  additional  will  purchase  the  horse  power  equipment.  A 
hand  power  plant  capable  of  drilling  50  per  cent,  deeper  than 
the  above  costs  about  $1,400. 

A  steam  power  plant  that  can  be  used  to  bore  a  ij^-in. 
hole  800  ft.  deep,  or  a  2^-in.  hole  (2-in.  core)  500  ft.  deep, 
costs  about  $2,400,  including  the  8  H.  P.  boiler  on  wheels ; 
the  drill  itself  costing  $1,100,  the  boiler  $400;  I  set  of  car- 
bons (9  carats),  $450,  and  the  balance  for  sundries.  The 
drill  itself  weighs  600  Ibs.,  but  the  full  outfit  packed  for  ship- 
ping weighs  10,000  Ibs. 

A  steam  power  plant  that  can  be  used  to  bore  a  I  ^-in.  hole 
1,500  feet,  or  a  2^-in.  hole  1,000  feet,  can  be  purchased  for 
$4,600;  of  which  $2,400  is  for  the  drill,  $500  for  the  15  H.  P. 
boiler  on  wheels,  $600  for  12  carats  of  carbons  and  the  bal- 
ance for  rods  and  sundries.  This  outfit  weighs  20,000  Ibs. 

Cost  in  Virginia. — There  is  a  great  deal  to  be  found  in 
print  relative  to  the  cost  of  diamond  drilling,  but  unfortu- 
nately the  records  as  published  are  in  such  form  as  to  be  oi 
far  less  value  than  they  should  be.  By  this  I  mean  that  any 
record  of  any  kind  of  drilling  to  be  of  great  value  should 
give :  ( i )  The  rate  of  penetrating  a  given  kind  of  rock  when 
the  drill  is  actually  cutting;  (2)  the  speed,  power  and  weight 
of  the  machine;  (3)  the  time  lost  in  raising  the  drill  to 
change  bits,  remove  cores,  or  the  like ;  (4)  the  time  required 
to  shift  from  one  hole  to  the  next;  (5)  the  average  time  lost 
in  repairs,  breakdowns,  etc. ;  (6)  the  diameter  and  depth  of 


98          ROCK  EXCAVATION— METHODS  AND  COST. 

hole;  (7)  the  time  consumed  in  driving  and  pulling  casing. 
No  record  in  print  contains  all  these  factors.  Strangely 
enough,  one  of  the  earliest  printed  accounts  contains  more 
of  these  factors  than  any  subsequent  record.  I  refer  to  an  ad- 
mirable paper  by  O.  J.  Heinrich,  in  Trans.  Am.  Inst.  Min., 
Eng.,  1874,  from  which  I  have  abstracted  the  following : 

The  diamond  drill  crew  consisted  of  three  men,  two  to  run 
the  drill  and  one  to  help  raise  the  drill  rods,  beside  a  fore- 
man. The  shift  was  12  hrs.  long,  and  the  following  was  the 
cost  of  operating  a  shift : 

Foreman,   or   boring   master    $2.50 

Mechanic,  or  engineer   2.00 

Assistant   1.50 

Laborer   .  i.oo 


Total  labor $7.00 

The  coal  consumed  was  10  Ibs.  per  H.  P.  per  hr.  For 
holes  up  to  1,000  ft.  deep  an  8  H.  P.  engine  was  used,  the 
drill  rods  weighing  4,500  Ibs.;  but  up  to  a  1,500- ft.  hole  a 
12  H.  P.  engine  was  used,  with  rods  weighing  7,000  Ibs.  The 
drill  had  a  2-in.  bit,  on  which  were  mounted  never  less  than 
12  carbons,  better  16.  The  drill  rods  were  raised  after  every 
10  ft.  of  drilling.  The  drilling  was  done  in  Chesterfield 
county,  Va.,  prospecting  for  coal,  in  1873.  The  cost  of  op- 
erating per  shift  is  given  as  follows : 

Labor     $6.50 

1/3  ton  coal  at  $3 i.oo 

Oil    0.50 

Diamonds  and  repairs   • n.oo 

Interest  and  deprec 1.92 


Total  per  day    . .  . $20.92 

The  price  of  carbons  was  $10  per  kt.  Rates  of  wages  were 
also  much  lower  then,  and  it  should  be  noted  that  the  allow- 
ance for  interest  and  depreciation  is  too  low  for  a  plant  cost- 
ing $7,200,  as  it  is  stated  this  8  H.  P.  plant  cost. 


COST  OF  DIAMOND  DRILLING.  99 

Depth  of  hole  in  earth  and  rock 419  850  1,142 

Depth  bored  in  rock 396  826  1,118 

No.  of  12-hr,  shifts  actually  boring 13.88  44.41  59.29 

"      "       "          "       raising  rods  15.87  59-34  Il6-46 

incidentals 3.25  15.25  68.25 

total 33.00  1 19.00  224.00 

Ft.  progress  per  hr.  while  boring 2.37  1.55  1.57* 

"      "    average   0.998  0.578  0.308 

Cost  of  labor,  per  ft $0.36  $0.59  $1.02 

Cost  of  fuel  ($3  ton)  per  ft $0.53  $0.14  $0.17 

Cost   of   all    other    items,    incl.    materials 

and  blacksmithing    $1.29  $1.43  $2.05 

Interest $0.16  $0.27  $0.38 

Total  cost  per  ft $1.86  $2.43  $3.62 

From  the  data  given  by  Mr.  Heinrich  I  have  prepared  the 
following  formulas  to  be  used  in  computing  the  number  of 
hours  required  to  drill  a  hole  of  given  depth. 

Let 

T  =  Total  number  of  minutes  required  to  bore  the  hole, 
n  =  total  depth  of  hole  in  feet. 

1  =  length  of  each  coupling  rod  =  10  ft.  in  this  case. 
t  =  the  number  of  minutes  required  to  bore  i  ft.  of  the 
hole.  In  the  formation  given  by  Heinrich  t  =  19 
mins.  per  ft.  of  hole  up  to  a  depth  of  300  ft.,  to 
which  add  5  mins.  per  ft.  for  each  100  ft.  of  in- 
creased depth. 

r  =  time  in  minutes  required  to  raise  and  lower  the  rods, 
including  2  mins.  to  uncouple  and  couple  up. 
r  =  7  mins.  for  hole  up  to  300  ft.  plus  1-3  min.  for 

each  additional  100  ft. 
s  =  number  of  lengths  of  coupling  rod. 
The  time  consumed  in  actual  boring  in  feet  is  obviously 
nt.     The  time  consumed  in  raising  and  lowering  the  drill 
rods  is  the  sum  of  an  arithmetical  series  in  which  s  =  the 
number  of  terms  and  r  =  the  common  difference ;  hence  the 

sum  is  l/2s  (2r  +  [s — i]  )r,  which   reduces  to — -  The 


[oo        ROCK  EXCAVATION— METHODS  AND  COST. 
total  time  is  therefore : 


2   12 

If  1=10 

T  =  nt  +  n(l°  +  n)  r 

200 

~  n3  r 

T  =  nt  +   ,  nearly. 

200 

For  holes  of  the  following  depths  we  have : 

ft.  ft.  ft. 

n  =        400  800  1,200 

t  (minutes)   r=          24  44  64 

r  (minutes)   =71/3  8  2/3  10 

T  (minutes)   =  14,300  63,000  148,800 

T  (hours)       =        240  1,050  2,480 

On  Heinrich's  work  about  10  per  cent,  more  time  than  the 
above  was  required  to  cover  losses  from  delays  arising  from 
various  causes.  The  point  that  is  strikingly  brought  out  by 
Heinrich's  records  is  the  rapid  falling  off  in  the  rate  of  speed 
of  drilling  each  foot  of  hole  with  increased  depth.  The 
cause  is  obvious,  however,  for  the  longer  the  line  of  drill  rods 
the  greater  the  friction  of  the  rods  upon  the  sides  of  the  drill 
hole,  and  consequently  the  slower  their  revolution  with  an 
engine  of  limited  horse  power.  The  increased  weight  of  the 
rods  with  increased  depth  also  reduces  the  rate  of  speed  with 
which  they  are  hoisted  by  the  engine ;  and  this  is  a  very  im- 
portant factor  in  adding  to  the  labor  and  fuel  cost  of  drilling 
deep  holes.  Heinrich's  estimates  of  the  time  required  to  drill 
holes,  including  all  10  per  cent,  allowance  for  delays,  are  as 
follows : 


COST  OF  DIAMOND  DRILLING.  101 

400- ft  hole,     288  hours 

800  "     "         960       " 
1,200  "     "      2,616       " 

It  will  be  observed  that  these  times  check  fairly  well  with 
the  times  obtained  by  applying  the  formula  that  I  have 
given ;  but  it  should  be  added  that  the  constants  in  the  for- 
mula need  further  verification  by  other  observers.  The  ma- 
terial penetrated  in  the  800- ft.  hole  was : 

Hard  silicious  sandstone 210  ft. 

Medium     "  "        362  " 

Argillaceous   sandstone   and   slate. 237  " 
Limestone    18  " 

Total  827  " 

Heinrich's  estimates  of  time,  and  my  own  formula  based 
thereon,  assume  a  uniform  sandstone  throughout  in  the 
three  holes.  Had  the  rock  been  uniform  throughout,  the 
cost  would  have  been : 

400- ft.  hole,  at  $1.26,   $504 

8oo-ft.      "       "    2.10,  i, 680 

i,200-ft.      "      "    4.00,  4,800 

Cost  in  Lehigh  Valley.— Mr.  L.  A.  Riley  is  authority  for 
the  following,  as  given  in  Trans.  Am.  Inst.  Min.  Eng.,  1876: 
Two  machines  belonging  to  the  Lehigh  Valley  Coal  Co. 
were  used.  A  No.  2  drill  with  16  H.  P.  boiler  and  1,000  ft. 
of  2-in.  rod  cost  $3,900,  which  with  diamonds,  etc.,  came 
to  $5,000;  the  weight  being  3,500  Ibs.  Carbons  cost  $9  per 
carat,  and  borts  cost  $11.  Five  diamonds  weighing  18 
carats  were  used  per  bit,  drilling  a  2-in.  hole  and  bringing 
up  a  i^2-in.  core.  There  were  24  holes,  aggregating  9,902 
ft.,  the  deepest  being  900  ft.  The  average  rate  of  drilling 
these  holes  was  19  ft.  per  day  per  machine,  at  an  average 
cost  of  $2.22  per  ft.  The  rock  was  a  very  hard  sandstone 
and  conglomerate.  The  force  on  each  drill  was  one  fore- 


102        ROCK  EXCAVATION— METHODS  AND  COST. 

man,  one  engineer  and  one  fireman.    The  average  cost  per 

ft.  of  hole  was : 

Labor $.1.15 

Diamonds 66 

Supplies  and  repairs 41 


Total  $2.22 

The  cost  of  the  900- ft.  hole  (the  deepest)  was  $1.95  per 
ft.,  which  indicates  that  with  a  powerful  (16  H.  P.)  engine 
there  is  no  such  great  increase  in  cost  per  ft.  with  increased 
depth  as  Heinrich  found  with  an  8  H.  P.  engine.  The  16- 
H.  P.  plant  used  by  Riley  was  capable  of  drilling  a  2,ooo-ft. 
hole.  Note  especially  that  both  Riley  and  Heinrich  paid 
less  than  $10  a  carat  for  carbons  and  that  Riley  does  not 
say  what  proportion  of  carbons  to  borts  were  used. 

Cost  on  Croton  Aqueduct. — Mr.  J.  P.  Carson,  in  Trans. 
Am.  Inst.  Min.  Eng.,  1890,  gives  the  following: 

Fourteen  holes,  total  2,084  ft.,  were  drilled  in  the  year 
1895. 

Actual   days   worked    189  days 

Moving  drill    15 

Idle     18 

Holidays  and  Sundays    39 

Total   261 

Daily  Progress  Cost 

Feet.  per  ft. 

347  ft.  Hard  gneiss                          n  to  12  $3-97 

814  ft.  Decomposed  gneiss           23.1  to  28  1.15 

572  ft.  Clay,  gravel  and  boulders    6.7  to  9  4.07 

351  ft.  Clay  and  gravel  25  


2,084  ft.                 Average                          10.2  2.91 

Crew,   i   foreman  @  $125  mo.;  I   assistant  foreman  @ 
$70 ;  4  men  @  $65. 
Wages,   8.1    mos $3>785 


COST  OF  DIAMOND  DRILLING.  103 

Team  moving $80 

66.7  tons  coal   ( 189  days)    360 

Supplies,  Diamond  Drill  Co 472 

Foundry    291 

Lumber,  rope,  etc 53 

Interest  on  $6,000  plant  @  12  per  cent.  8.1  mos..  .  486 

Renewing  diamonds   250 

Diamond  bit  lost    300 


Total,  204  days  $6,077 

Aver,  per  day  $29.79 

Aver,  per  ft $  2.91 

Note  that  the  interest  on  the  plant  is  altogether  too  low. 

Cost  of  Hand  Diamond  Drilling  in  Arizona. — Eng.  News, 
Jan.  18,  1900,  p.  34,  Mr.  J.  B.  Lippincott  gives  data  on  dia- 
mond drilling  at  the  Gila  River  Dam  site,  Arizona.  The  ma- 
chinery was  in  two  distinct  parts,  (i)  the  hand  pile  driver 
for  sinking  casing  pipe  to  bed  rock;  (2)  the  diamond  drill. 
The  hammer,  made  by  the  Pierce  Well  Co.,  120  Liberty 
street,  New  York,  is  in  sections,  so  that  its  weight  can  be 
varied  up  to  190  pounds ;  it  is  raised  by  a  hand  winch,  and 
tripped  by  nippers;  maximum  drop  11^2  ft.  A  tool-steel 
head  is  screwed  into  the  top  of  the  pipe  and  receives  the 
blow.  The  pipe  is  3^2,  2^  and  2  in.,  extra  heavy,  screw 
pipe,  5  ft.  sections,  with  extra  heavy  couplings  which  have 
beveled  edges.  When  the  casing  has  reached  bed  rock,  the 
sand  inside  is  removed  by  using  a  chopping  bit  and  a  water 
jet.  The  bit  is  screwed  to  a  ^-in.  pipe  through  which  water 
is  pumped  by  a  hand  pump,  the  water  passing  out  through 
holes  in  the  bit,  thus  bringing  the  sand  to  the  top  of  the  cas- 
ing. In  this  manner  a  casing  pipe  130  ft.  deep  can  be 
cleaned  of  sand  and  gravel.  If  a  boulder  is  struck,  after 
the  diamond  drill  has  penetrated  it,  four  or  five  sticks  of 
dynamite  are  lowered  and  discharged,  shattering  the  boul- 
der so  that  the  casing  can  be  driven  down. 

The  diamond  drill  was  made  by  the  American  Diamond 
Rock  Drill  Co.,  New  York  City.  One  inch  core  bits  were 


104        ROCK  EXCAVATION— METHODS  AND  COST. 

usually  employed.  The  drill  was  operated  by  hand  power, 
six  men  being  employed  on  this  work  as  well  as  on  driving 
the  casing.  The  drill  will  penetrate  200  ft.  into  rock,  and 
will  make  6  to  8  ft.  per  day  in  hard  rock  and  10  to  15  ft.  per 
day  in  soft  rock;  The  plant  complete  costs  $1,000,  including 
two  diamond  bits  worth  $200  each,  set  with  six  I -carat  dia- 
monds each.  Two  machines  were  used.  The  pipe  cost  $600 
and  freight,  $100. 

Cost  of  operation  per  month,  foreman   $150. 

6  laborers  at  $1.50  for  28  days, 234. 

i  cook   45. 

$429 
240  rations  at  60  cts 144 


Total  labor  for  one  month   $573 

Total  repairs,  pipe  and  lumber  for  one  party  for  10 

months    500 

Team,  feed,  etc 350 

Moving 670 

Sundry  incidentals   430 

Supervision    350 


Total  supplies,  etc.,  for  10  mos $2,300 

Total  labor,   10  mos 5>73° 


Total    $8,030 

Total  number  of  feet  sunk    3>254 

Cost  per  ft $2.46 

52   holes,   cost  per  hole    $154.42 

Total  Depths  Penetrated. 
Earth,ft.          Rock,  ft.          Total,ft. 

The  Buttes   1,621.2  196.0  1,817.2 

Queen  Creek    357.8  55.6  413.4 

Riverside     .  ,>. . .      729.8  40.2  770.0 

Dykes 80.0  o.o  80.0 

San  Carlos   143.2  30.4  173.6 

2,932.0  322.2  3>254-2 


COST  OF  DIAMOND  DRILLING.  105 

A  month's  time  of  one  party  was  lost  due  to  continual 
breaking  of  the  casing  pipe  under  the  hammer.  Note  that 
90  per  cent,  of  the  drilling  did  not  involve  the  use  of  dia- 
monds but  consisted  in  driving  through  the  earth  covering 
overlying  the  rock.  This  is  characteristic,  however,  of  test- 
ing dam  sites. 

References. — As  stated  in  the  fore  part  of  this  chapter, 
diamond  drilling  data  are  to  be  found  in  abundance. 
Among  the  most  vauable  of  articles  relating  to  the  cost  of 
diamond  drilling  are  the  following :  In  Engineering  News, 
Apr.  2,  1903,  data  of  drilling  in  South  Africa ;  in  Engineer- 
ing News,  July  23,  1903,  is  an  excellent  account  of  the  cost 
of  drilling  test  holes  (100  ft.  deep),  along  the  line  of  a  pro- 
posed canal  in  New  York  State ;  in  the  Transactions  of  the 
Institution  of  Mining  and  Metallurgy,  Apr.  23,  1903,  Mr. 
J.  N.  Justice  gives  valuable  cost  data  of  drilling  deep  holes 
(460  to  1,627  ft.),  on  the  coast  of  Africa ;  in  Mines  and  Min- 
erals there  are  several  excellent  articles  by  Lane,  in  the  last 
half  of  the  year  1899;  in  Engineering  Magazine,  March, 
1896,  there  is  a  good  article  by  Channing,  an  engineer  who 
has  had  much  experience  in  Michigan ;  in  the  catalogues  of 
American  manufacturers  of  diamond  drills  much  valuable 
information  is  given. 


CHAPTER  VII. 
EXPLOSIVES. 

The  Action  of  Gases  from  an  Explosion. — The  explosives 
in  common  use  in  America  are  few  in  number:  Black 
powder,  several  varieties  of  dynamite,  Judson  powder  and 
Joveite.  In  every  case  an  explosion  is  a  chemical  action  that 
takes  place  between  the  elements  of  the  explosive,  liberating 
suddenly  a  great  volume  of  gas  at  a  high  temperature.  Ordi- 
nary air  moving  at  a  velocity  of  100  miles  an  hour  strikes 
objects  with  great  disruptive  force,  yet  a  hurricane  is  mild 
indeed  compared  with  the  feeblest  of  explosives.  Black 
powder,  which  is  the  weakest  of  the  common  explosives,  is 
exploded  whenever  it  reaches  a  temperature  of  518°  F.  If 
its  grains  are  small,  as  in  rifle  powder,  each  grain  quickly 
burns  up,  yielding  the  full  volume  of  gas  in  a  short  time. 
If  its  grains  are  larger  the  rapidity  with  which  each  grain 
is  converted  into  gas  is  slower. 

Dynamite  and  Jovite  are  exploded  not  by  mere  heating, 
as  with  black  powder,  but  by  a  hard  shock  delivered  usually 
by  a  cap,  or  "detonator,"  or  "exploder."  The  more  severe 
the  blow  delivered  by  the  exploding  of  the  cap,  the  more 
quickly  does  the  chemical  action  take  place.  In  any  case 
this  chemical  action  is  far  more  rapid  than  it  is  in  black 
powder,  but  the  greater  the  shock  the  more  rapid  is  the  lib- 
eration of  the  gases.  Hence  it  is  poor  economy  to  use 
feeble  caps  where  it  is  desired  to  tear  rock  into  small  pieces. 

If  a  quantity  of  dynamite  is  exploded  under  water  it  has 

1 06 


EXPLOSIVES.  to? 

been  found  by  actual  experiment  that  the  gases  fly  in  all  di- 
rections with  equal  velocity  and  in  equal  quantity.  *  Hence 
it  is  a  mistake  to  suppose  that  high  power  explosives  act 
only  downward.  They  exert  a  pressure  equal  in  all  di- 
rections at  the  instant  of  explosion.  Let  it  be  kept  clearly 
in  mind  that  an  explosion  is  merely  the  sudden  creation  of 
a  great  volume  of  gas  seeking  to  escape  with  enormous  ve- 
locity, and  much  of  the  mystery  about  the  effects  of  an  ex- 
plosion vanishes.  Consider  the  gas  as  so  many  minute  and 
invisible  rubber  balls,  each  possessed  of  weight  and  flying 
with  frightful  velocity,  and  it  becomes  comparatively  easy 
to  explain  most  of  the  phenomena  attending  an  explosion. 
The  gas  as  it  leaves  the  explosive  flies  in  all  directions,  but 
the  instant  it  encounters  an  object  it  either  rebounds  from 
that  object,  or  tears  its  way  through  the  object,  or  hurls  the 
object  to  one  side.  If  the  object  is  very  heavy  and  sub- 
stantial, the  particles  of  gas  rebound  from  it,  like  rubber 
balls  rebounding  from  the  side  of  a  house.  Hence  it  often 
happens  that  the  gases  from  dynamite,  when  exploded  in 
an  open  place,  travel  along  a  certain  path  like  a  hurricane. 
They  do  so  because  they  have  rebounded  from  some  im- 
movable objects,  and  have  been,  as  it  were,  reflected  like 
rays  of  light  from  a  mirror. 


*  Eng.  News.  March  12,  1892,  "D.  E.  O."  in  a  letter  states  that  in  1878,  near 
Sawyer  City,  Pa.,  a  wagon  containing  60  qts.  of  nitroglycerine  overturned,  and 
the  nitroglycerine  exploded.  The  writer  gives  a  sketch  to  show  the  wedge  path 
of  the  exploded  gases.  The  writer  says:  "Take  two  2  or  3-oz.  bottles  and  fill 
with  nitroglycerine,  fit  one  with  an  exploder  and  let  the  exploder  rest  on  the 
bottom  of  the  bottle;  place  this  on  a  sheet  of  boiler  iron  and  explode.  It  will 
be  found  to  have  barely  brightened  the  plate.  Now  fit  No.  2  with  an  exploder 
fastened  in  the  neck  of  the  bottle  and  explode,  and  it  will  be  found  to  have 
blown  a  hole  completely  through  the  plate."  The  writer  contends  that  this 
experiment  proves  that  dynamite  does  not  exert  an  equal  pressure  in  all  direc- 
tions when  exploded.  The  editor  of  Engineering-  News  cites  the  extensive  ring- 
gage  tests  conducted  by  Gen.  Henry  L.  Abbot  "with  nitroglycerine  under 
water."  A  s-ft.  ring  carried  six  pressure  gages,  and  to  record  pressure  of  dyna- 
mite fired  at  the  center  of  the  ring.  The  charge  was  placed  in  a  tin  can,  placed 
vertically,  and  was  fired  at  the  top  by  a  detonator.  The  ring  was  suspended  in 
a  vertical  plane  from  buoys.  At  a  depth  of  35  ft.,  the  two  upper  gages  regis- 
tered 20,366  and  17,576  Ibs.  per  sq.  in.,  and  the  two  lower  15,479  and  14,671 
Ibs.  In  a  later  experiment,  16,000  and  21,000  Ibs.  were  recorded  in  the  upper 
gages;  and  15,000  and  16,000  Ibs.  in  the  lower. 


io8        ROCK  EXCAVATION— METHODS  AND  COST. 

When  dynamite  is  exploded  in  a  hole  drilled  in  solid  rock, 
the  gases  are  created  so  suddenly  and  move  with  such  enor- 
mous velocity  that  when  they  strike  the  sides  of  the  drill 
hole,  the  rock  is  struck  as  if  with  a  mighty  sledge;  and,  if 
the  dynamite  is  in  sufficient  quantity,  the  blow  tears  off  a 
portion  of  the  rock.  This  occurs  even  when  the  hole  above 
the  dynamite  is  not  plugged  up  with  earth  or  stone  chips; 
but  if  the  hole  is  left  open  obviously  much  of  the  gas  es- 
capes and  renders  the  blow  less  effective  in  consequence. 
Black  powder,  on  the  other  hand,  explodes  more  slowly  so 
that  if  the  hole  is  left  open  a  greater  proportion  of  the  gas 
escapes  before  the  last  grain  of  powder  has  burned  up. 
Hence  it  is  absolutely  essential  to  use  great  precaution  in 
plugging  the  hole  where  black  powder  is  to  be  fired. 

In  the  early  days  of  dynamite  it  was  commonly  stated 
that  no  "tamping"  above  the  dynamite  was  required,  and 
to  this  day  there  are  text  books  in  use  containing  this  mis- 
leading statement.  Tamping  may  not  be  "required,"  in 
the  sense  that  it  is  absolutely  essential;  but  it  is  certainly 
required  where  the  full  value  of  the  dynamite  is  to  be  utilized 
in  breaking  rock,  instead  of  disturbing  the  air,  for  there  is 
no  profit  in  shaking  up  the  atmosphere. 

Due  to  the  fact  that  powder  gases  are  elastic,  and  rebound 
from  any  solid  surface,  it  follows  that  the  shape  of  the  drill 
hole  has  a  decided  effect  upon  the  lines  along  which  rock 
breaks.  When  holes  are  drilled  by  hand  they  tend  to  be- 
come three  cornered;  and  as  a  result,  if  black  powder  is 
used,  the  particles  of  gas  bouncing  back  and  forth,  as  fast 
as  they  are  liberated,  batter  the  three  faces  of  the  triangle 
and  tend  to  split  the  rock  in  three  directions,  the  cracks  in 
the  rock  starting  at  the  corners,  or  angles  of  the  triangle. 

Black  Powder. — The  highest  grade  of  black  powder  con- 
sists of  75  per  cent,  saltpeter  (KNO3),  15  per  cent,  charcoal 
and  10  per  cent,  sulphur.  The  charcoal  for  rifle  powder 
(sporting  powder)  is  commonly  made  from  dogwood,  but 
willow  and  alder  charcoal  are  commonly  used  for  blasting 


EXPLOSIVES.  109 

powder.  In  some  inferior  powders  lampblack  is  substituted 
for  part  of  the  charcoal.  The  saltpeter  (or  nitre)  is  often 
replaced  by  sodium  nitrate  (Na  NO3),  which  deteriorates 
in  time  by  absorbing  moisture  from  the  air.  Therefore 
when  blasting  powder  containing  sodium  nitrate  ("soda 
powder")  is  used,  great  care  must  be  taken  to  keep  it  in  a 
dry  atmosphere,  and  it  should  be  used  very  soon  after  it  is 
received  from  the  factory.  Powder  is  sold  by  the  "keg"  of 
25  Ibs.,  at  about  $1.25  a  keg  for  soda  powder  and  $2.10  for 
nitre  powder.  The  specific  gravity  of  individual  grains  of 
black  powder  ranges  from  1.5  to  1.85;  the  average  weight 
of  loose  powder,  slightly  shaken,  being  62^  Ibs.  per  cu.  ft., 
or  i  Ib.  occupies  28  cu.  ins. 

Properties  of  Good  Black  Powder. — A  good  blasting 
powder  has  a  uniform  dark  gray  or  slaty  color.  A  dead 
black,  or  a  bluish  color,  indicates  either  too  much  charcoal 
or  the  presence  of  moisture.  When  poured  over  a  sheet  of 
white  paper  it  should  leave  no  dust,  for  dust  indicates  either 
the  presence  of  moisture  or  of  fine  mealy  powder.  The  size 
of  the  grains  should  be  quite  uniform,  and  should  have  no 
sharp  or  angular  corners.  On  pressing  between  the  fingers 
there  should  not  be  a  crackling  sound  due  to  sharp  grains, 
nor  should  the  grains  crush  easily!  When  crushed  the  grains 
should  show  the  same  uniformity  of  color.  Light  colored 
spots  in  the  powder  show  that  the  saltpeter  has  leached  out, 
due  to  the  presence  of  moisture,  which  reduces  the  strength 
and  reliability  of  the  powder.  If  there  are  no  white  spots 
it  may  be  assumed  that  the  powder  has  not  suffered  from 
dampness ;  so  that  if  it  is  slightly  damp  but  still  uniform  in 
color  it  can  be  dried  out  in  the  sun  and  will  be  as  good  as 
ever.  A  pinch  of  good  powder  ignited  on  a  sheet  of  white 
paper  burns  away  rapidly,  leaving  no  residue.  If  black  spots 
remain  on  the  paper  they  show  an  excess  of  charcoal  or 
poor  mixing  of  the  ingredients.  Yellow  spots  indicate  an 
excess  of  sulphur.  If  holes  are  burned  in  the  paper  they  in- 
dicate an  excess  of  moisture,  or  other  imperfections. 


no        ROCK  EXCAVATION— METHODS  AND  COST. 

Dynamite  and  Nitroglycerin. — Any  explosive  containing 
nitroglycerin  is  commonly  called  dynamite.  Nitroglycerin 
is  made  by  mixing  I  to  I  1-6  parts  of  pure  glycerin  with  3 
parts  of  nitric  acid  and  5  parts  sulphuric  acid.  The  glyc- 
erin is  added  very  slowly,  with  constant  stirring,  com- 
pressed air  usually  being  used  to  stir  the  liquids.  The  proc- 
ess of  manufacture  is  exceedingly  dangerous.  Nitroglycerin 
is  an  oily  fluid  as  clear  as  water  when  perfectly  pure,  but  it 
usually  has  a  yellowish  tint.  Its  specific  gravity  is  1.6,  so 
that  it  weighs  nearly  0.058  Ib.  per  cu.  in.,  or  102  Ibs.  per  cu. 
ft.  It  freezes  at  about  38°  F.  (water  freezes  at  32°),  and 
instead  of  swelling  as  water  does  on  freezing,  it  shrinks 
about  8  per  cent,  in  volume.  Nitroglycerin  evaporates  rapid- 
ly at  158°  F. ;  and  even  at  104°  dynamite  will  lose  10  per 
cent,  of  its  nitroglycerin  in  the  course  of  a  few  days.  Hence 
the  necessity  of  keeping  dynamite  in  a  cool  place  in  sum- 
mer, and  in  a  warm,  but  not  too  warm,  place  in  winter.  In 
small  quantities  it  will  ignite  and  burn  up  without  exploding 
at  356°  F.,  but  at  423°  F.  it  explodes  violently.  In 
large  quantities,  heated  slowly,  it  will  explode  at  356°  F. 
If  the  nitroglycerin  is  impure  it  will  explode  at  lower  tem- 
peratures. Indeed  it  is  possible  for  impurities  to  start  a 
chemical  decomposition  which  will  result  in  a  rise  in  tem- 
perature ending  in  spontaneous  explosion. 

If,  after  the  mixture  of  the  ingredients,  every  trace  of 
acid  is  not  washed  out  of  the  nitroglycerin,  there  is  an  ever- 
present  danger  of  chemical  action  in  the  nitroglycerin  that 
may  lead  to  an  explosion  upon  the  slightest  provocation. 
Chemical  decomposition  usually  liberates  nitrous  fumes 
which  color  the  nitroglycerin  green.  If  there  is  any  green- 
ish color  in  dynamite  it  indicates  that  chemical  action  has 
begun  and  that  the  material  is  dangerous  to  handle.  Free 
acid  in  nitroglycerin  can  be  detected  by  blue  litmus  paper 
which  the  acid  turns  to  red.  In  order  to  destroy  deterio- 
rated nitroglycerin  pour  it  into  a  strong  solution  of  sal  soda 
(sodium  carbonate)  and  stir  gently  with  a  wooden  paddle. 


EXPLOSIVES.  in 

Pure  nitroglycerin  has  been  carried  by  a  rocket  to  a 
height  of  i  ,000  ft.  and  dropped  without  exploding  upon 
striking  the  earth.  Yet  the  purest  of  nitroglycerin  is  liable 
to  explode  by  shock  if  it  is  confined  in  a  vessel.  When  im- 
pure it  will  explode,  even  when  unconfined,  upon  receiving 
a  slight  shock.  A  small  quantity  of  nitroglycerin  will  burn 
quietly  without  exploding;  but  where  a  large  quantity  is 
burning  the  heat  generated  will  bring  the  entire  mass  to  a 
temperature  at  which  an  explosion  will  occur. 

On  account  of  its  sensitiveness  to  shock  when  slightly  im- 
pure, nitroglycerin  is  not  used  for  blasting  to  any  great  ex- 
tent nowadays.  It  is  used  in  its  liquid  state  chiefly  for 
"shooting"  oil  wells,  so  as  to  open  up  crevices  in  the  rock 
through  which  the  oil  may  flow  to  the  well.  The  nitroglyc- 
erin is  poured  into  tin  "shells,"  3  to  5  ins.  diam.  by  5  to  20 
ft.  long,  and  lowered  with  a  wire  to  the  bottom  of  the  well 
hole.  An  iron  weight  with  a  hole  through  its  center  is  strung 
on  the  .wire  and  allowed  to  drop,  thus  exploding  a  cap  on 
the  cover  of  the  "shell." 

Varieties  of  Dynamite. — Dynamite  consists  of  any  ab- 
sorbent or  porous  material  saturated  or  partly  saturated 
with  nitroglycerin.  The  absorbent  is  commonly  called 
"dope."  A  good  dope  should  have  minute  voids  in  which 
the  nitroglycerin  is  held  by  capillary  action.  Since  the  dope 
acts  like  a  cushion  it  renders  the  nitroglycerin  much  less 
sensitive  to  shocks.  If  40  per  cent,  of  the  weight  of  the 
dynamite  is  nitroglycerin  it  is  known  as  a  "40  per  cent, 
powder" ;  if  75  per  cent,  it  is  a  "75  per  cent,  powder."  The 
word  "powder"  is  commonly  used  instead  of  the  word  dyna- 
mite, and,  in  consequence,  it  often  confuses  the  hearer  or 
reader  who  is  at  a  loss  to  know  whether  black  powder  or 
dynamite  is  meant. 

The  following  are  some  of  the  well-known  dynamites: 


ii2        ROCK  EXCAVATION— METHODS  AND  COST. 

ATLAS  POWDER   (75  per  cent.) 

Nitroglycerin   75  parts. 

Wood   fiber    21       " 

Sodium  nitrate 2 

Magnesium  carbonate    2 

RENDROCK  (40  per  cent.) 

Nitroglycerin   40  parts. 

Potassium  nitrate   40       " 

Wood   pulp    13       " 

Pitch   7       " 

GIANT  POWDER  No.  2  (40  per  cent.) 

Nitroglycerin   40  parts. 

I  Sodium  nitrate    40       " 

Sulphur 6       " 

Resin 6       " 

Kieselguhr   8       " 

STONITE   (68  per  cent.) 

Nitroglycerin   68  parts. 

Kieselguhr   20       " 

Wood  meal    4       " 

Potassium  nitrate   8       " 

DUALIN  (40  per  cent.) 

Nitroglycerin   40  parts. 

Sawdust   30       " 

Potassium    nitrate    30       " 

CARBONITE   (25  per  cent.) 

Nitroglycerin   25  parts. 

Woodmeal     40^  " 

Sodium  nitrate 34       " 

Sodium  carbonate   l/2  " 

HERCULES  (40  per  cent.) 

Nitroglycerin   40  parts. 

Potassium  nitrate   31       " 

Potassium  chlorate    3  1-3  " 

Magnesium  carbonate   10 

Sugar    i52-3u 


EXPLOSIVES.  113 

VIGORITE  (30  per  cent.) 

Nitroglycerin   3°  parts. 

Potassium  chlorate  49 

Potassium  nitrate   7 

Wood  pulp 9 

Magnesium  carbonate   5 

HORSLEY  POWDER  (72  per  cent.) 

Nitroglycerin   72  parts. 

Potassium  chlorate 6 

Nutgalls    i 

Charcoal   21 

GELIGNITE  (62^  per  cent.) 

65  per  cent,  of  blasting  gela-  I     Nitroglycerin,  96  per  cent, 
tin,  containing  j    Collodion  cotton,  4  per  cent. 

^|      Sodium  nitrate,  75  per  cent. 

35  per  cent,   of  absorbent,  ^  Sodium  carbonate  :  per  cent. 
containing  j      Wood  pulp)  ^  per  cent 

FORCITE  (49  per  cent.) 

50  per  cent,  of  blasting  gel-  )    Nitroglycerin,  98  per  cent, 
atin,  containing  \    Collodion  cotton,  2  per  cent. 

Sodium  nitrate  76  per  cent. 


50  per  cent,   of   absorbent, 
containing 


Sulphur,  3  per  cent. 
Wood  tar,  20  per  cent. 


Wood  pulp  i  per  cent. 
JUDSON  GIANT  POWDER  No.  2  (40  per  cent.) 

Nitroglycerin   40  parts. 

Sodium    nitrate    . . 40       " 

Resin 6       " 

Sulphur 6      " 

Kieselguhr   8 

VULCANITE  (30  per  cent.) 

Nitroglycerin   30  parts. 

Sodium  nitrate 

Sulphur 7 

Charcoal  


ii4        ROCK  EXCAVATION— METHODS  AND  COST. 

Many  of  the  "powders"  above  named  are  made  with  dif- 
ferent percentages  of  nitroglycerin.  A  "No.  I  powder"  or- 
dinarily contains  75  per  cent,  of  nitroglycerin;  and  a  "No.  2 
powder,"  40  per  cent,  nitroglycerin;  but  the  manufacturers 
have  a  great  variety  of  letters  and  numbers  to  denote  the 
different  grades  of  "powder."  The  following  table  indi- 
cates how  varied  is  the  numbering  and  lettering  of  the  dif- 
ferent grades  made  by  different  firms: 

Aetna  Powder,  No.  I          65  per  cent. 

"       No.  2XX   50 

"       No.  2      40 

"       No.  3X      35        " 

"       No.  4X      25 

"      No.  5         15        « 

Atlas   Powder  A 75 

B+ 60 

B 50        " 

C+ 45 

C 40        " 

D+ 35        " 

D 30        " 

E+ 25        " 

E 20 

F+ 15        " 

Dynamite   (Nobel's)   Old  No.   1 75  per  cent. 

"      No.  2 40 

"      No.  3 25        - 

The  Absorbent. — Alfred  Nobel,  who  invented  dynamite 
in  1866,  used  porous,  earthy  powder,  called  kieselguhr,  as 
the  absorbent  to  hold  the  liquid  nitroglycerin  in  its  pores, 
somewhat  as  a  sponge  holds  water.  Kieselguhr  is  a  diato- 
maceous  earth  which  consists  of  the  silicious  remains  of  mi- 
croscopic plants  called  diatoms.  These  diatoms  contain 
microscopic  pores  or  cells  which  hold  the  nitroglycerin  by 
capillary  action.  Of  late  years  sodium  nitrate  and  wood 
pulp  have  been  very  largely  substituted  for  kieselguhr. 


EXPLOSIVES.  115 

I  find  in  the  Census  Report  for  1900  that  in  the  annual 
production  of  42,900  tons  of  dynamite  there  were  used: 
15,800  tons  of  nitroglycerin,  20,000  tons  of  sodium  nitrate, 
5,000  tons  of  wood  pulp  and  240  tons  of  ammonium  nitrate. 
It  will  be  seen  from  this  report  that  dynamites  with  an  inert 
base  or  "dope"  of  kieselguhr,  or  magnesium  carbonate,  are 
no  longer  made  in  America;  and  that  dynamites  with  an 
explosive  base  of  the  nitrate  class  have  taken  their  place.  It 
will  also  be  seen  that  the  nitroglycerin  used  averages  about 
38  per  cent,  of  the  weight  of  the  dynamite  as  now  manufac- 
tured. 

Weight  of  Dynamite. — Dynamite  is  commonly  packed 
in  paper  cartridges,  each  "stick"  being  about  6  to  10  ins. 
long  and  of  a  diameter  to  slip  readily  into  the  hole.  The 
most  common  size  of  stick  is  1^4  ms-  diam.  by  8  ins.  long, 
weighing  l/2  to  6-10  Ib.  Dynamite  is  shipped  in  cases,  or 
boxes,  holding  50  Ibs.  of  dynamite,  and  must  be  packed  and 
marked  in  accordance  with  the  rules  prescribed  by  the  rail- 
road over  which  it  is  to  travel.  Not  every  user  of  dynamite 
knows  that  an  act  of  Congress  (1851)  provides  that: 

"Any  person  or  persons  shipping  explosives  without  de- 
livering at  the  time  of  shipment  a  note  in  writing  expressing 
the  nature  and  character  of  such  merchandise  shall  for- 
feit to  the  United  States  $1,000." 

The  old  Nobel's  75  per  cent,  dynamite,  with  the  kiesel- 
guhr "dope,"  weighs  .054  Ibs.  per  cu.  in.  The  following  table 
gives  the  weight  of  75  per  cent,  keiselguhr  dynamite: 

Weight  of  Nobel's  No.  I  dynamite  (75  per  cent,  nitrogen 
and  25  per  cent,  kieselguhr)  : 

Diam.         Weight  in  Ibs.        Diam.         Weight  in  Ibs. 
of  stick,      per  inch  of  stick,     of  stick,    per  inch  of  stick. 
I  in.  .042  1^4  .128 

i%  ins.  .065  2  .168 

i^  ins.  094  2*4  .212 

The  manufacturers  of  "Atlas  C"  inform  me  that  a  i%  x 
8-in.  stick  weighs  about  0.6  Ib.,  and  that  it  is  one  of  the 


ii6        ROCK  EXCAVATION— METHODS  AND  COST. 

"tricks  of  the  trade"  to  make  the  absorbent  of  such  material 

at  all  grades  of  dynamite  weigh  about  the  same  per  stick 
iJ4  x8in.). 

Thawing  Dynamite. — The  nitroglycerin  in  dynamite 
freezes  at  42°  to  46°  F.,  according  to  the  character  of  the 
"dope."  When  frozen  it  cannot  be  exploded  by  the  ordinary 
caps  used  in  blasting;  nevertheless  in  its  frozen  state  it  is 
exceedingly  sensitive  to  friction  or  to  any  breaking  or  cut- 
ting of  the  frozen  cartridge.  The  Annual  Report  for  1898 
of  the  Inspectors  of  Explosives  of  Great  Britian  states  that 
in  1898  there  were  81  accidents  in  thawing  dynamite,  result- 
ing in  killing  68  men  and  injuring  97.  Accidents  from 
other  causes  were  194  in  number,  resulting  in  the  killing  of 
52  men  and  the  injury  of  216.  This  shows  in  a  striking 
manner  how  dangerous  a  process  the  thawing  of  dynamite 
is.  The  following  are  a  few  of  the  methods  of  thawing 
that  are  given  in  the  report  as  having  led  to  injury  or 
death : 

Some  cartridges  being  thawed  on  a  stone  in  a  weigh  house ;  thaw- 
ing cartridges  in  front  of  a  kitchen  fire ;  thawing  dynamite  on  a 
shovel;  cartridges  placed  near  a  fire  to  thaw;  cartridges  placed  in  LH 
oven  to  thaw ;  hot-water  thawer,  containing  dynamite  placed  on  a 
blacksmith's  fire;  thawing  dynamite  with  a  candle;  warming  dyna- 
mite over  a  blacksmith's  fire;  heating  dynamite  in  a  tin  over  a 
candle;  rubbing  cartridge  in  hands  to  complete  thawing;  cartridge 
left  in  pocket  of  trousers,  which  were  hung  before  fire  to  dry ;  thaw- 
ing dynamite  in  water  over  a  fire;  nine  separate  accidents  from  re- 
heating water  which  had  been  used  in  a  dynamite  thawer,  averaging 
one  killed  and  one  injured  for  each  accident. 

I  have  italicized  this  last  mentioned  cause  of  accident,  be- 
cause in  my  judgment  it  is  at  the  base  of  the  great  majority 
of  all  accidents  from  thawing  dynamite.  It  shows  that  the 
nitroglycerin  leaks  out  of  the  dynamite  especially  when  sub- 
ject to  heat  in  the  presence  of  water.  Dynamite  should 
never  be  thawed  by  plunging  the  sticks  into  warm  water. 
Nitroglycerin  will  often  leak  out  of  a  stick  even  when  the 
stick  is  dry  but  is  subjected  to  heat.  This  I  have  actually 
seen.  In  driving  a  prospect  tunnel  in  Idaho  it  was  our  cus- 


EXPLOSIVES.  H7 

torn  to  thaw  dynamite  in  the  oven  of  a  cook-stove;  but, 
when  the  thawing  did  not  progress  rapidly  enough,  we 
would  hold  sticks  of  dynamite  in  our  hands  over  the  top  of 
the  stove.  While  doing  this  one  day  I  noticed  that  a  drop 
of  nitroglycerin  had  leaked  through  the  folds  of  the  paper 
cartridge  and  was  about  to  fall  upon  the  stove.  In  my  haste 
to  move  the  stick  away  the  drop  fell  upon  the  hot  stove,  ex- 
ploding with  a  report  like  a  pistol  shot  and  cracking  the 
stove  so  badly  that  live  coals  fell  into  the  oven.  The  dyna- 
mite in  the  oven  immediately  began  to  burn  up  with- 
out exploding.  It  is  perhaps  needless  to  add  that  those 
of  us  who  were  in  the  cabin  went  out  during  the  time  that 
the  dynamite  was  baking.  As  stated  in  previous  paragraphs, 
free  nitroglycerin  is  exceedingly  sensitive  to  shock  and  heat 
combined,  and  one  drop  of  it  falling  even  a  short  distance 
upon  any  hot  object  will  explode,  and  by  its  explosion  set 
off  any  sticks  of  dynamite  nearby. 

Mr.  E.  E.  R.  Tratman  has  cited  an  instance  where  dyna- 
mite sticks  were  placed  on  a  canvas  cover  over  a  pot  of 
boiling  water ;  nitroglycerin  leaked  out,  and  through  the  can- 
vas settled  on  the  bottom  of  the  pot,  where  it  exploded,  the 
water  above  it  acting  as  a  tamping. 

A  man  working  for  me  laid  some  sticks  of  75  per  cent, 
dynamite  upon  a  flat  stone  which  he  had  previously  heated 
by  placing  hot  coals  upon  it.  While  in  the  act  of  picking  up 
a  handful  of  thawed  sticks  he  was  blown  to  atoms.  With- 
out doubt  the  cause  was  the  leaking  out  of  a  drop  of  nitro- 
glycerin which,  falling  upon  the  hot  stone,  exploded  the  re- 
.naining  sticks.  He  was  using  this  method  directly  con- 
trary to  orders,  because  he  had  "thawed  dynamite  all  his 
life  in  that  way."  Familiarity  breeds  contempt  for  the 
danger  ever  present  in  thawing  dynamite,  and  the  manager 
of  blasting  operations  must  not  rely  merely  upon  orders  to 
the  men  not  to  do  this  or  that,  but  must  be  vigilant  to  ob- 
serve whether  orders  are  obeyed  or  ignored.  Instant  dis- 


ii8        ROCK  EXCAVATION— METHODS  AND  COST. 

charge  of  an  employee  should  be  the  punishment  for  the 
slightest  infraction  of  rules  governing  the  use  of  explosives. 

Dynamite  can  be  ignited  with  a  match,  and  will  usually 
burn  up  without  exploding,  provided  that  there  are  only  a 
few  sticks  not  confined  in  any  way.  This  fact  has  had  much 
to  do  with  breeding  contempt  for  the  danger  attending 
thawing.  Low-grade  dynamites  (40  per  cent,  and  under) 
are  safer  to  thaw  than  high-grade  dynamites,  because  the 
"dope"  is  not  so  thoroughly  saturated  with  nitroglycerin,  and 
for  that  reason  is  not  so  apt  to  "leak" ;  but  in  the  presence 
of  hot  water  any  grade  of  dynamite  will  have  its  nitro- 
glycerin displaced  slowly  by  the  water.  In  fact,  if  the  manu- 
facturers are  not  careful  to  remove  every  trace  of  water 
from  the  nitroglycerin  there  is  danger  of  "leaking."  When 
the  paper  cartridges  feel  greasy  it  is  due  to  leakage  of 
nitroglycerin.  When  a  whitish  crust,  or  efflorescence,  is 
found  on  the  outside  of  a  dynamite  cartridge  it  indicates 
that  the  dynamite  has  been  stored  in  a  damp  place,  or  that 
the  "dope"  originally  contained  an  excess  of  moisture.  In 
either  case  the  crust  is  nitrate  of  soda  that  has  dissolved  out, 
and  such  dynamite  is  almost  certain  to  leak  nitroglycerin. 
It  is  unreliable,  dangerous  to  handle,  and  should  be  de- 
stroyed at  once.  Greenish  stains  inside  the  cartridge  indi- 
cate that  the  nitroglycerin  is  decomposing  and  is  dangerous. 

I  have  laid  particular  stress  upon  the  leaking  of  nitro- 
glycerin from  dynamite,  because  it  is  so  common  a  source 
of  accident  and  because  the  fact  that  dynamite  can  be  ex- 
ploded under  water  has  lead  many  to  infer  that  water  has 
no  deleterious  effect  upon  it.  Dynamite  under  water  begins 
to  part  with  its  nitroglycerin  immediately,  the  water  slowly 
replacing  the  nitroglycerin  in  the  "dope,"  and  even  in  cold 
water  a  few  hours  of  soaking  will  materially  decrease  the 
percentage  of  nitroglycerin.  In  warm  water  the  replace- 
ment is  much  more  rapid. 

How  to  Thaw  Dynamite. — We  have  seen  how  dangerous 
it  is  to  thaw  dynamite  by  plunging  the  sticks  into  hot  water 


EXPLOSIVES.  119 

or  by  allowing  live  steam  to  strike  the  sticks,  due  to  the 
fact  that  the  water  forces  the  nitroglycerin  out  of  the  stick ; 
and  we  have  seen  how  sensitive  such  free  nitroglycerin  is 
to  slight  shocks,  especially  when  hot.  We  have  seen  how 
exceedingly  dangerous  it  is  to  place  dynamite  upon  a  stove, 
or  in  front  of  an  open  fire,  or  upon  the  top  of  a  steam 
boiler,  or  upon  a  hot  stove.  How,  then,  can  dynamite  be 
thawed  with  comparative  safety? 

Green  manure  is  an  effective  and  safe  material  to  use  in 
thawing  dynamite.  On  the  Croton  Dam  work  the  follow- 
ing method  was  used:  A  cubical  box  2,y2  ft.  on  a  side  is 
set  inside  a  box  16  ins.  larger  on  a  side,  and  the  8-in.  space 
filled  with  manure  rammed  hard.  These  two  boxes  are 
placed  in  a  cubical  hole  in  the  ground  and  15  ins.  of  loosely 
rammed  manure  is  packed  around.  The  floor  of  this  maga- 
zine is  filled  to  a  depth  of  10  ins.  with  hard  rammed  manure, 
leaving  a  remaining  space  that  easily  holds  50  Ibs.  of  dyna- 
mite. The  lid  is  provided  with  a  pipe  chimney  2^  ft.  long, 
having  a  sliding  cover  for  ventilation.  The  dynamite  is 
piled  in  loosely,  the  lid  closed  and  manure  covered  over  it 
to  a  depth  of  12  ins.  The  ventilator,  as  a  rule,  is  left  slightly 
open,  and  at  32°  F.  outside  the  powder  will  thaw  in  3  to  5 
hrs. ;  at  o°  F.  outside  it  will  thaw  in  8  hrs.  This  thaw  box 
is  cheap,  simple  and  safe.  The  manure  on  the  bottom  of 
this  magazine  acts  as  a  cushion  to  absorb  any  nitroglycerin 
that  might  leak  out.  It  is  necessary  to  change  all  the 
manure  occasionally. 

I  am  not  favorably  impressed  with  any  method  of  thaw- 
ing that  involves  standing  the  sticks  of  dynamite  on  end, 
for  that  facilitates  the  leakage  of  nitroglycerin.  I  have  seen 
a  box  of  dynamite  that  had  been  stored  on  its  end  in  a 
magazine,  and  the  nitroglycerin  had  leaked  from  the  cart- 
ridges saturating  the  wood  of  the  box. 

The  plan  of  placing  a  can  of  hot  water  in  a  small  thawing 
magazine  is  one  of  the  safest  methods  that  can  be  adopted. 
Such  a  method  is  illustrated  in  Fig.  7,  page  120. 


120        ROCK  EXCAVATION— METHODS  AND  COST. 

Where  a  very  large  quantity  of  dynamite  must  be  thawed 
daily,  a  small  thaw-house  should  be  built  with  several  doors 


ENQ.  NEWS 


Plan. 


Fig.  7. 


in  front,  and  tiers  of  drawers  that  slide  out  should  be  placed 
immediately  back  of  the  doors,  so  that  a  man  cannot  enter 
the  thaw-house  itself  from  the  front.  This  prevents  men 
from  loitering  in  the  thaw-house,  and  possibly  standing  in- 
side to  light  a  pipe.  The  dynamite  is  laid  in  the  drawers 
(6  ins.  deep  x  16  x  22. ins.)  on  a  thin  bed  of  sawdust.  In 
the  rear  of  the  thaw-house,  back  of  the  drawers,  room  is 
left  for  a  small  hot  water  radiator  such  as  is  used  in  house 
heating;  i-in.  pipes  lead  from  this  radiator  to  the  hot  water 
heater  which  is  some  distance  away  from  the  thaw-house, 
in  a  separate  building  entirely,  so  that  there  is  no  chance 
for  the  thaw-house  to  be  set  on  fire.  Under  no  condition 
use  steam  to  heat  the  thaw-house.  A  temperature  greater 
than  that  of  boiling  water  (212°)  should  not  by  any  pos- 
sibility be  reached  inside  the  house. 

The  foregoing  are  the  only  methods  of  thawing  dyna- 
mite permitted  by  the  Municipal  Explosives  Commission  in 
New  York  City,  namely,  thawing  with  manure,  and  thaw- 
ing in  a  dry  chamber  heated  by  hot  water  entirely  separate 
from  the  fire  that  heats  the  water. 


EXPLOSIVES.  121 

Testing  Dynamite  for  Safety. — The  outside  of  dynamite 
cartridges  should  not  feel  greasy,  nor  should  there  be  a 
trace  of  free  nitroglycerin  inside  the  wrapper.  In  order  to 
determine  whether  a  stick  is  leaky,  dry  it  on  a  clean  sheet 
of  brown  paper  in  a  room  at  60°  to  80°  F.  for  about  12 
hours.  An  oily  discoloration  on  the  brown  paper  shows 
that  nitroglycerin  has  leaked  out.  Good  dynamite  will  show 
no  such  discoloration  of  the  paper. 

Dynamite  that  has  been  frozen  and  thawed  a  number  of 
times  often  leaks,  although  before  the  freezing  and  thawing 
it  did  not  leak  at  all.  Hence  a  few  sticks  should  be  frozen 
and  thawed  three  successive  times  and  then  tested  for  leak- 
iness  on  brown  paper  as  above  explained. 

Long-continued,  high  temperature  will  develop  leakiness 
in  a  poor  quality  of  dynamite.  Hence  a  few  samples  should 
be  kept  at  a  temperature  of  85°  to  90°  F.  for  six  consecu- 
tive days  and  nights,  and  then  tested  for  leakiness  on  brown 
paper  as  above  explained. 

A  whitish  crust  on  dynamite  sticks  indicates  that  it  has 
been  damp  and  that  the  nitrate  of  soda  or  potash  has  leached 
out  (effloresced)  ;  and  that  consequently  the  dynamite  is 
no  longer  reliable,  and  may  fail  to  explode  in  blasting,  beside 
being  dangerous  to  handle.  If  the  dynamite  inside  the 
wrapper  shows  greenish  spots  it  indicates  decomposition  of 
the  nitroglycerin,  and  consequently  is  exceedingly  dan- 
gerous. 

Blasting  Gelatin. — Soluble  guncotton  dissolved  in  nitro- 
glycerin gives  a  jelly-like  substance  of  yellow  color  known 
as  blasting  gelatin.  It  has  a  specific  gravity  of  1.6  and 
freezes  at  35°  to  40°  F.  as  compared  with  42°  to  46°  at  which 
dynamite  freezes.  It  is  far  more  dangerous  than  dynamite 
when  frozen,  being  more  sensitive  to  shocks  in  the  frozen 
condition  than  when  soft.  It  is  peculiarly  adapted  for  use 
in  tropical  climates  or  in  summer  work,  since  it  does  not 
absorb  water  and  does  not  leak  under  any  conditions,  even 
after  long  exposure  to  90°  F.,  nor  does  it  leak  after  re- 


122        ROCK  EXCAVATION— METHODS  AND  COST. 

peated  freezing  and  thawing.    In  cold  weather  its  extreme 
sensitiveness  when  frozen  makes  it  exceedingly  dangerous. 

Gelatin  dynamite  is  an  explosive  containing  blasting  gela- 
tin and  an  explosive  "dope."  Forcite  and  gelignite  are  the 
two  best  known  gelatin  dynamites.  They  are  apt  to  leak 
and  should  be  tested  precisely  as  ordinary  dynamite  is  tested 
for  leakage  by  repeated  freezing  and  thawing  and  by  pro- 
longed exposure  at  90°  F. 

Judson  Powder  and  Contractors'  Powder. — Judson  powder 
consists  of: 

Nitroglycerin   5  per  cent. 

Sodium  nitrate 64    " 

Sulphur  16   " 

Cannel  coal 15    " 

The  "contractor's  powder"  made  by  the  Aetna  Powder 
Co.  is  similar,  but  it  contains  8  per  cent,  nitroglycerin.  They 
are  both  free  running  black  powders  made  honey-combed 
so  as  to  hold  a  small  percentage  of  nitroglycerin,  and  are 
fired  with  caps  or  exploders  exactly  as  dynamite  is  fired. 
They  are  sold  in  5O-lb.  boxes. 

Joyeite. —  Joveite  is  a  free-running,  dry  powder  resem- 
bling corn  meal  in  appearance.  It  does  not  freeze,  nor  has 
it  ever  been  found  to  deteriorate  upon  exposure  to  heat.  It 
is  composed  of  nitro-napthalene,  nitro-phenol  and  nitrate  of 
soda.  Recently  the  manufacturers  have  succeeded  in  mak- 
ing it  perfectly  waterproof.  I  have  seen  it  charged  in  holes 
full  of  water  and  exploded  without  a  misfire.  The  manu- 
facturers have  made  strong  claims  not  only  for  the  effective- 
ness of  this  powder  in  competition  with  dynamite,  but  for 
the  far  greater  safety  attending  its  use.  The  fact  that  it 
does  not  freeze  alone  entitles  it  to  consideration  as  a  "safety 
explosive,"  but  it  can  also  be  fired  into  with  rifle  bullets, 
hammered  with  iron  on  iron,  burned  up  by  lighting  it  with 
a  match,  heated  to  the  burning  point  with  electric  sparks 
from  a  powerful  static  electric  machine,  and  otherwise  sub- 
jected to  the  most  severe  tests  without  exploding.  It  will 


EXPLOSIVES.  123 

burn  up  quietly  when  a  certain  temperature  is  reached,  but 
it  takes  a  strong  cap,  placed  not  further  than  half  an  inch 
from  the  stick  of  explosive,  to  explode  it.  I  have  personally 
subjected  Joveite  to  these  and  other  tests  for  safety,  and  am 
convinced  that  it  is  incomparably  the  safest,  reliable  ex- 
plosive in  the  market  to-day.  Joveite  has  been  in  extensive 
use  for  about  five  years,  and  as  yet  no  accident  has  occurred 
in  using  it.  I  have  fired  an  iron  projectile  from  a  mortar 
loaded  with  a  weighed  quantity  of  Joveite,  and  have  found 
it  superior  to  dynamite  in  hurling  power,  grade  for  grade. 
Joveite  is  manufactured  in  four  grades,  each  grade  being 
equal  to  the  various  grades  of  20  per  cent,  to  60  per  cent, 
dynamite. 

I  have  inhaled  the  gases  resulting  from  exploding  Joveite 
without  suffering  from  the  headache  that  follows  such  a 
test  with  dynamite;  from  which  it  would  appear  that  it 
would  be  less  objectionable  than  dynamite  in  underground 
work. 

Joveite  can  be  poured  into  dry  holes  like  Judson  or  black 
powder,  but  ordinarily  it  is  charged  in  paper  cartridges  ex- 
actly as  dynamite  is  charged,  and  fired  by  the  same  kind  of 
caps  or  exploders.  In  its  action,  Joveite  is  a  trifle  "slower" 
than  dynamite,  but  when  the  higher  grades  are  used  it  breaks 
the  rock  into  smaller  fragments. 

On  the  great  rock  excavation  work  now  in  progress  at 
the  New  York  Central  yards  in  New  York  City  I  find  that 
Joveite  has  displaced  dynamite  and  is  doing  more  efficient 
work  in  the  tough  rock  encountered  there,  and  at  less  cost 
than  dynamite.  The  same  holds  true  of  several  of  the  large 
trap  rock  quarries  near  New  York  City.  I  am  able,  there- 
fore, to  agree  with  Prof.  Courtney  De  Kalb,  of  the  School 
of  Mining,  Kingston,  Ontario,  who,  in  his  excellent  little 
"Manual  of  Explosives,"  says :  "Joveite  has  been  tested  by 
the  ablest  explosive  experts  and  has  never  proven  unsafe  or 
unreliable.  It  would  seem  to  fulfil  all  the  requirements  of 
an  ideal  explosive." 


CHAPTER  VIII. 
CHARGING  AND  FIRING. 

Kind  of  Explosive  to  Use. — Whether  a  high  power  or  a 
low  power  explosive  is  to  be  preferred  is  dependent  largely 
upon  the  use  to  which  the  rock  is  to  be  put,  as  well  as  upon 
the  strength  of  the  rock  itself.  Black  powder,  with  its 
comparatively  slow,  heaving  action,  is  used  where  the  ma- 
terial is  quite  friable,  as  in  mining  coal  or  galena,  or  in  ex- 
cavating shale,  hardpan  and  the  like.  It  is  also  used  in  small 
charges  placed  in  a  row  of  holes  where  it  is  desired  to  wedge 
off  blocks  of  ''dimension  stone"  for  building  purposes. 

Judson  powder  (which  contains  a  small  percentage  of 
nitroglycerin)  is  considerably  more  powerful  than  black 
powder,  and  is  used  in  open  cut  excavation  where  the  rock 
is  of  medium  strength.  It  is  also  used  in  "chamber  blast- 
ing," where  large  charges  of  it  are  placed  at  the  end  of  a 
small  tunnel  and  a  mountain  of  rock  dislodged  at  one  shot. 
In  such  cases  it  will  break  up  very  hard  rock,  leaving  it,  how- 
ever, in  large  chunks. 

A  high  power  explosive  like  dynamite  is  invariably  used 
in  tunnel  driving,  shaft  sinking  and  open-cut  work  in  tough 
rock.  Specifications  usually  prohibit  the  use  of  dynamite  for 
quarrying  dimension  stone,  because  it  is  apt  to  shatter  the 
stone.  For  quarrying  stone  to  be  used  as  rubble,  especially 
if  the  stone  is  tough  and  occurs  in  massive  layers,  dynamite 
can  usually  be  used  without  danger  of  injuring  the  stone.  A 
40  per  cent,  dynamite  is  commonly  used  in  open  cut  work, 
but  with  tough  rock  it  often  pays  to  use  a  50  to  75  per  cent, 
dynamite  (or  the  equivalent  grade  of  Toveite)  especially  if 
the  rock  is  to  be  shattered  so  that  it  will  pass  through  a 

124 


CHARGING   AND   FIRING.  125 

crusher  or  is  to  be  loaded  with  a  steam  shovel.  I  have  found 
it  advantageous  to  begin  blasting  in  open  cuts  by  using  40 
per  cent,  dynamite.  If  the  rock  comes  out  in  too  large 
chunks  then  to  every  three  sticks  of  40  per  cent,  powder  I 
use  one  stick  of  75  per  cent.;  and  in  successive  blasts  in- 
crease the  proportion  of  75  per  cent,  until  the  rock  comes 
out  in  chunks  of  desirable  size.  Experiments  should  also 
be  made  in  spacing  the  holes,  but  of  this  I  will  speak  more 
at  length  later.  Having  found  the  proportion  of  40  per 
cent,  to  75  per  cent,  dynamite  yielding  the  best  results,  it  is 
possible  to  order  a  grade  of  dynamite  that  will  contain  the 
desired  percentage  of  nitroglycerin.  Thus,  assuming  that 
the  best  charge  is  two  sticks  of  40  per  cent,  to  one  stick  of 
75  per  cent.,  we  have  : 

2  X  40  per  cent.  =  80 
i  X  75  Per  cent-  =  75 


J55  ~^~  3  —  52  Per  cent.,  which  is  approximately  the  grade 
of  powder  to  order.  If  the  job  is  small,  one  can  continue 
to  use  a  mixture  of  40  per  cent,  and  75  per  cent,  dynamite, 
but  on  large  work  it  involves  too  much  trouble  to  use  two 
grades  of  powder  in  the  same  hole.  Moreover,  the  75  per 
cent,  dynamite  is  far  more  dangerous  to  handle,  particularly 
where  it  must  be  thawed.  Managers  and  foremen  are  prone 
to  do  all  their  experimenting  by  changing  the  spacing  of  the 
drill  holes  or  by  changing  the  weight  of  the  explosive  used 
in  the  charges,  instead  of  experimenting  to  determine  the 
most  effective  grade  of  explosive  to  use. 

In  tunneling,  the  "cut  holes"  are  frequently  charged  with 
75  per  cent,  dynamite,  and  the  "trimming  holes"  with  40 
per  cent,  dynamite.  In  tunneling  through  weak  rock,  like 
shale,  40  per  cent,  dynamite  will  be  found  powerful  enough 
even  for  the  "cut  holes."  Vast  sums  of  money  are  daily 


126        ROCK  EXCAVATION— METHODS  AND  COST. 

wasted  in  the  mines  and  quarries  of  the  United  States 
through  lack  of  systematic  experimenting  to  determine  the 
most  economic  grade  of  explosive  and  the  most  economic 
spacing  of  drill  holes.  By  taking  the  work  of  blasting  tem- 
porarily out  of  the  hands  of  my  foreman  I  have  repeatedly 
succeeded  in  reducing  the  "powder  bill"  from  10  per  cent, 
to  35  per  cent.,  and  I  do  not  hesitate  to  say  that  a  foreman 
who  can  be  trusted  to  select  the  proper  grade  of  explosive 
intellegently  is  "one  in  a  Hundred." 

Charging  Black  Powder. — After  pumping  out  the  sludge, 
the  hole  is  made  perfectly  dry  by  a  "wiper,"  using  cotton 
waste  or  hay  held  by  a  spiral  twist  at  the  end  of  the  "wiper." 
The  other  end  of  the  "wiper"  is  often  provided  with  a  small 
spoon  for  scraping  out  the  sludge  at  the  bottom  of  the  hole. 
If  the  hole  is  a  small  one  the  powder  may  be  poured  through 
a  tin  funnel  with  a  long  stem  reaching  to  the  bottom  of  the 
hole,  so  that  none  of  the  powder  lodges  upon  the  sides.  In 
large,  deep  holes  no  such  precautions  are  taken.  If  the  hole 
is  horizontal  the  powder  may  either  be  shoved  in  in  paper 
bags,  or  a  long  spoon-like  scoop  may  be  used  to  deliver  the 
powder  to  the  end  of  the  hole  where  it  is  dumped  by  re- 
volving the  handle  of  the  scoop.  A  safety  fuse  should  be 
used  (or  electric  cap),  and  its  lower  end  should  be  well 
buried  in  the  powder.  If  paper  cartridges  are  used,  the  end 
of  the  fuse  is  shoved  into  the  powder  and  the  paper  tied 
around  it ;  but  do  not  pull  the  string  so  tightly  as  to  pinch  the 
fuse  so  as  to  break  the  powder  thread  inside  it.  If  the  hole 
is  a  wet  one,  a  waterproof  cartridge  must  be  used.  To  make 
such  a  cartridge,  fold  a  long  strip  of  brown  paper  spirally 
around  a  wooden  mandril,  slightly  smaller  than  the  diameter 
of  the  drill  hole,  at  its  lower  end,  letting  the  edges  of  the 
paper  overlap  well.  Before  removing  the  paper  from  the 
mandril,  dip  it  into  melted  paraffine,  giving  it  several  coats. 
In  a  very  wet  hole  another  spiral  paper  wrapping  in  the  re- 
verse direction,  well  paraffined,  will  insure  dryness.  Load 
this  cartridge  with  powder,  attach  the  fuse  and  immerse  in 


CHARGING  AND   FIRING.  127 

melted  paraffine  (113°  F.).  This  cartridge  will  be  perfectly 
water  tight,  but  cannot  be  rammed. 

After  the  drill  hole  is  loaded  a  tamping  of  clay  or  sand  is 
used  to  fill  the  hole.  The  kind  of  tamping  has  a  very  great 
effect  in  determining  the  force  of  the  explosion  of  black 
powder.  Clay  is  unquestionably  better  than  sand  and  should 
be  used  for  the  first  few  inches  anyway.  Dry  clay  is  first 
pressed  down  with  a  wooden  tamp  rod.  Never  use  a  metal 
rod  and  never  ram  the  tamping  at  the  start,  for  fear  of  an 
explosion.  Follow  with  ordinary  damp  clay  pressed  firmly 
to  place,  and  after  a  thickness  of  three  inches  of  tamping 
is  over  the  powder,  ram  by  tapping  the  end  of  the  tamping 
rod  with  a  hammer.  In  holes  i  in.  in  diam.  the  charge  will 
not  blow  out  if  there  are  7  ins.  of  good  tamping.  In  general 
the  tamping  will  not  blow  out  if  it  is  7  to  10  times  as  long 
as  the  hole  is  wide.  Nevertheless  the  tamping  should  be 
carried  to  the  surface  of  the  rock  if  the  greatest  effect  of 
the  powder  is  desired.  If  there  are  any  spaces  between  the 
powder  and  the  sides  of  the  hole,  or  between  the  powder 
and  the  tamping,  the  effect  is  to  cushion  the  blow  of  the  ex- 
plosion. In  quarrying  dimension  stone  this  cushioning  ef- 
fect is  sometimes  desirable,  and  it  is  purposely  secured  by 
filling  several  inches  of  the  hole  above  the  powder  with  hay, 
tow  or  the  like,  followed  by  several  inches  of  clay  tamped 
lightly,  and  finally  by  well  packed  tamping.  This  is  called 
"expansion  tamping." 

In  firing  black  powder  by  electricity,  electric  exploders  of 
low  power  are  used.  There  is  no  advantage  in  using  power- 
ful detonators,  because  black  powder  cannot  be  detonated, 
but  explodes  in  the  same  way  whether  a  match  or  an  elec- 
tric spark  or  another  explosive  fires  it. 

Charging  Dynamite. — The  charge  should  fill  completely 
the  part  of  the  hole  that  it  occupies,  and  should  be  packed 
solid.  Experiments  show  that  even  a  slight  air  cushion 
greatly  weakens  the  force  of  the  explosive  blow.  Since  the 
sticks  of  dynamite  are  slightly  smaller  in  diameter  than  the 


128        ROCK  EXCAVATION— METHODS  AND  COST. 

hole,  the  paper  of  the  cartridges  (excepting  the  last  one) 
should  be  slit  lengthwise  with  a  knife  *  and  after  each 
stick  is  dropped  or  pushed  into  the  hole,  press  it  well  home 
with  a  wooden  rammer.  If  there  is  standing  water  in  the 
hole  do  not  break  the  paper  of  the  cartridge,  and  do  not 
ram,  but  use  a  cartridge  that  will  just  fill  the  hole.  In  wet 
holes  it  is  well  also  to  daub  grease  over  the  cartridge  wher- 
ever water  might  enter  through  a  fold  in  the  paper.  The 
cartridges  should  never  be  so  large  as  to  require  forcing  to 
get  them  to  the  bottom  of  the  hole.  Remember  that  a  drill 
hole  tapers  toward  the  bottom.  Dynamite  should  never  be 
rammed,  but  merely  pressed  home ;  and  a  steel  or  iron  tamp- 
ing rod  should  never  be  used  for  this  purpose.  The  last 
stick,  or  "primer,"  is  provided  with  either  a  fuse  cap  or  an 
electric  detonator.  If  a  fuse  is  used  a  common  way  of  load- 
ing- is  first  to  slip  the  end  of  the  fuse  into  the  cap,  bite  the 
end  of  the  cap  shell  so  as  to  pinch  it  upon  its  fuse ;  and,  if 
the  blaster  survives  this  part  of  the  operation,  the  next  step 
is  to  dig  a  hole  in  the  middle  of  the  dynamite  stick  with  a 
wire  nail;  push  the  cap  into  the  hole  and  pinch  the  plastic 
dynamite  around  it;  take  a  half-hitch  with  the  fuse  around 
the  dynamite  cartridge  and  lower  it  or  push  it  to  place.  A 
cap  should  never  be  crimped  onto  the  fuse  with  anything 
but  a  "crimper"  made  for  the  purpose.  A  half-hitch  in  the 
fuse  is  quite  apt  to  break  the  powder  thread  inside  the  fuse 
and  thus  cause  a  misfire.  If  an  electric  exploder  is  used, 
taking  a  half-hitch  with  the  fuse  wires  is  apt  to  result  in 
breaking  one  of  the  wires  away  from  the  platinum  bridge  to 
which  it  is  soldered,  and  thus  causing  a  misfire.  An  expert, 
however,  who  is  skilful  and  careful  may  use  the  half-hitch 
without  causing  misfires.  The  method  recommended  in  all 
catalogues  of  manufacturers  is  first  to  open  the  end  of  the 


*  Never  cut  with  a  knife  or  otherwise  rupture  a  stick  of  dynamite  that  is 
frozen  or  partly  frozen.  Some  authorities  recommend  using  a  copper  blade 
instead  of  steel,  because  the  steel  might  strike  a  spark  if  there  were  any  grit  in 
the  cartridge. 


CHARGING   AND   FIRING.  129 

"primer"  cartridge  by  folding  back  the  paper;  then  to  in- 
sert the  cap  part  way  into  the  dynamite  after  boring  a  little 
hole  in  the  dynamite  with  a  wooden  stick  with  a  rounded 
point.  The  cap  is  left  projecting  about  ^  in.  above  the 
dynamite,  so  that  by  no  chance  can  the  fuse  set  fire  to  the 
dynamite  and  thus  reduce  the  force  of  the  explosion.  The 
ends  of  the  paper  cartridge  are  drawn  up  around  the  fuse 
or  the  fuse  wires,  and  tied  with  a  string  as  in  Fig.  8,  one  end 
of  the  string  being  left  long  enough  to  let  the  "primer"  down 
to  the  bottom  of  the  drill  hole.  In  any  case  the  cap  should 
fit  tightly  in  the  dynamite,  for  even  a  slight  air  space  will 
serve  as  a  cushion  to  reduce  its  force  and  so 
weaken  the  force  of  the  final  explosion.  In 
wet  holes,  smear  grease  around  the  end  of  the 
cap.  The  end  of  the  fuse  should  be  cut  square 
across,  preferably  with  a  "fuse  cutter,"  and 
then,  holding  the  fuse  upright,  slip  the  cap 
over  it.  It  should  require  no  effort  at  all  to 
slip  the  cap  on,  for  either  pressing  or  twisting 
the  cap  on  may  explode  it.  If  the  fuse  is  too 
large  whittle  it  down  with  a  knife;  if  too 
small,  wrap  paper  around  it.  Crimp  the  shell 
of  the  cap  about  ^  in.  from  its  end  with  the 
"crimper,"  which  is  combined  with  the  "fuse 
cutter."  At  the  other  end  of  the  fuse  cut  a  slit 
y2  in.  long  to  expose  the  powder  core  for 
lighting  with  a  candle  flame  or  torch.  Dry 
paper  may  be  twisted  around  the  end  to  insure 
lighting,  but  it  is  not  good  practice  to  soak 
cloth  or  waste  in  oil  and  wrap  it  around  the 
fuse.  Of  course  the  end  of  the  fuse  should 
not  be  allowed  to  drop  into  water,  at  least 
not  until  the  fire  inside  has  crept  some  distance  down 
into  the  fuse.  The  "primer"  should  not  be  lowered  into  the 
hole  by  the  fuse,  because  in  this  way  the  cap  is  often  pulled 
loose  leaving  an  air  cushion  that  greatly  reduces  the  force 


130        ROCK  EXCAVATION— METHODS  AND  COST. 

of  the  explosion.  When  the  "primer"  has  been  lowered  it 
should  never  be  compressed  or  rammed;  but  the  tamping 
should  be  placed  upon  it  immediately. 

To  emphasize  the  importance  of  inserting  a  cap  and  fuse 
in  the  end  rather  than  in  the  side  of  a  stick,  a  quotation  from 
a  paper  by  Mr.  A.  W.  Warwick  in  Mines  and  Minerals 
will  serve: 

"There  was  no>  doubt  in  my  mind,  after  studying  the 
method  of  loading,  that  there  was  a  possibility  of  the  burn- 
ing fuse  setting  fire  to  the  dynamite  cartridge  on  top  of  the 
primer  before  exploding  the  cap.  In  order  to  see  if  this 
were  the  case  or  not,  a  piece  of  pipe  12  in.  in  length  and  ^ 
in.  in  diameter  was  obtained,  a  piece  of  fuse  was  passed 
through  and  a  cork  was  forced  in  so  as  to  hold  the  dyna- 
mite; a  stick  of  dynamite  was  squeezed  into  the  pipe  and 
held  in  place  by  a  plug.  The  fuse  was  fired  and  develop- 
ments were  awaited  at  a  respectful  distance.  Out  of  seven- 
teen experiments  six  resulted  in  an  explosion.  The  fumes 
from  the  explosion  were  very  acrid,  dense  and  rather  ruddy 
in  color.  The  nitroglycerin  was  fired  by  heat  and  not  by  de- 
tonation, and  the  fumes  had  the  appearance  and  odor  of 
fumes  generated  by  incomplete  combustion." 

The  best  tamping  is  dry  clay  or  bits  of  shale,  and  even 
where  sand  is  used  for  the  major  portion  of  the  hole  it  will 
pay  to  use  clay  balls  for  the  first  foot  or  so,  the  clay  being 
moist  enough  to  roll  into  pellets.  A  handful  or  two  of  sand 
may  be  poured  into  the  hole  first  to  cover  the  "primer" ;  and 
then  follow  with  clay.  The  clay  pellets  should  be  lightly 
compressed  for  the  first  6  ins.,  and  above  that  the  tamping 
may  be  compressed  with  increasing  force.  Sand  is  gen- 
erally used  for  tamping  above  the  first  foot  or  two  because 
it  can  be  poured  in  with  much  greater  rapidity.*  Experi- 
menting with  different  kinds  of  tamping  on  any  given  class 
of  work  is  time  'and  money  well  spent,  for  it  is  not  a  fact 
that  dynamite  needs  no  tamping,  or  that  water  makes  a  good 

*  I  would  suggest  pouring  enough  water  into  the  hole  after  the  sand  is  in  to 
dampen  it,  for  damp  sand  arches  better  than  dry  sand  and  better  resists  the 
pressure. 


CHARGING   AND   FIRING.  131 

tamping.  Mr.  W.  L.  Saunders  is  authority  for  the  statement 
that  one  pound  of  dynamite  under  a  water  tamping  will  not 
do  as  much  execution  as  one-quarter  of  a  pound  in  dry  blast- 
ing. Bear  in  mind  that  tamping  is  cheaper  than  dynamite  even 
if  several  dollars  a  ton  are  paid  for  tamping  imported  by  rail. 
While  working  the  tamping  rod  with  the  right  hand,  hold 
the  fuse  or  the  fuse  wires  with  the  left  hand  so  as  to  detect 
and  thus  avoid  rubbing  the  fuse  with  the  tamping  rod.  Some 
blasters  use  a  tamping  rod  with  a  beveled  end,  and  hold 
the  rod  so  that  the  sharp  edge  of  the  bevel  is  always  on  the 
side  of  the  hole  farthest  from  the  fuse.  To  know  which 
side  the  sharp  end  is  on,  cut  a  longitudinal  groove  in  the 
tamping  rod. 

Some  authorities  recommend  placing  the  "primer"  at  the 
bottom  of  the  charge,  instead  of  at  the  top ;  others  say  that 
the  "primer"  should  be  placed  at  the  middle  of  the  hole. 
Dynamite  explodes  with  such  suddeness  that  we  may  well 
doubt  whether  it  makes  any  difference  at  all  where  the 
primer  is  placed,  so  far  as  the  execution  is  concerned.  It 
is  often  advisable,  in  deep  holes,  to  place  the  dynamite  in 
several  distinct  charges  separated  by  tamping,  and  in  this 
case  each  charge  should  have  its  own  cap  and  "primer"; 
but  this  is  a  matter  quite  aside  from  the  present  discussion 
and  will  be  taken  up  later. 

Handling  dynamite  sticks  with  the  bare  hands  will  give 
a  headache  to  anyone  not  used  to  it,  because  of  the  nitro- 
glycerin  absorbed  through  the  pores  of  the  skin.  The  ob- 
vious preventative  is  to  wear  gloves. 

Judson  powder  is  charged  like  black  powder,  but  it  is" 
fired  by  using  a  "primer"  consisting  of  a  stick  of  dynamite 
in  which  a  blasting  cap  is  imbedded.  Joveite  is  charged  and 
fired  like  dynamite. 

Firing  by  Electricity. — In  New  York  City  it  is  now  com- 
pulsory to  fire  all  blasts  by  electricity  on  account  of  the 
greater  safety  of  electric  firing.  Electric  firing  is  not  only 
safer  than  fuse  firing,  but,  in  open  cut  work  especially,  it  is 
more  effective,  because  the  simultaneous  explosion  of 


132       ROCK  EXCAVATION— METHODS  AND  COST. 

charges  in  a  row  of  holes  obviously  reduces  the  work  to 
be  done  by  each  charge  as  compared  with  fuse  firing  by 
which  one  charge  explodes  in  advance  of  the  neighboring 
charge.  In  tunneling,  where  the  center  cut  holes  must  be 
fired  in  advance  of  the  outer  holes,  it  will  probably  continue 
to  be  the  practice  to  fire  by  fuse,  using  fuses  of  different 
lengths  so  as  to  regulate  the  order  in  which  the  charges  in 
the  different  holes  will  explode,  but  there  are  few  places 
outside  of  tunnels  and  shafts  where  fuse  firing  is  preferable 
to  electric  firing  from  any  point  of  view ;  and  even  in  tunnel 
work  there  are  many  blasters  who  prefer  electric  firing. 

For  firing  by  electricity  the  electric  detonator,  A  (Fig.  9), 
is  placed  in  the  "primer,"  and  the  fuse  wires,  B,  are  car- 
ried up  along  the  "primer"  and  tied  with  a  cord,  C,  to  the 
"primer."  The  fuse  wires  attached  to  each  cap  are  fur- 
nished by  the  manufacturers  in  varying  lengths  to  suit 
varying  depths  of  drill  holes ;  but  it  is  not  necessary  to  have 
fuse  wires  that  will  reach  to  the  mouth  of  the  drill  hole,  for 

connecting   wires   may  be  spliced  on 

*  to  the  ends  of  the  fuse  wires  and  the 

1  splice  wrapped  with  insulating  tape. 

~J%^  '.Ljl^  When  a  splice  is  to  be  made  thus,  it 
is  well  to  cut  3  or  4  inches  off  one  of 
the  fuse  wires  so  that  one  splice  will 
not  come  directly  opposite  the  other ; 
for  when  this  is  done  it  is  necessary 
to  wrap  insulating  tape  around  one 
of  the  splices  only,  and  it  is  not  nec- 
essary to  wrap  even  one  splice  except 
in  damp  holes.  A  splice  is  made  by 
cutting  the  insulating  material  away 
for  2  or  3  ins.  back  of  the  ends  of  the 
wires  to  be  joined,  scraping  the  wires 

•IB ;  until    they    are    bright,   and    twist- 

ing   the    clean    wires    together,    as 
shown   in   Fig.    10.     Insulating  tape 


Fig.  9. 


CHARGING   AND   FIRING.  133 

is  y2  to  34  in.  wide  and  comes  in  J^-lb.  rolls.  It  is 
often  used  to  cover  splices  made  in  connecting  wires 
when  the  splice  comes  in  contact  only  with  dry  rock  on  dry 


Fig.  10. 

earth.  Practically  no  electricity  can  leak  through  dry  rock 
or  earth,  so  that  there  is  no  necessity  of  insulating  the  splices 
unless  the  bare  wire  is  apt  to  come  in  contact  with  moist 
earth  or  water.  The  fuse  wires  from  each  hole  are  con- 
nected right  and  left  with  the  fuse  wires  from  the 
neighboring  holes,  so  as  to  form  a  continuous  cir- 
cuit with  the  holes  in  series  (Fig.  n);  then  the 
end  of  the  fuse  wire  of  the  hole  on  the  extreme  left  is 
connected  with  a  "leading  wire"  that  runs  to  the  electric 


Bcrff-ery 


battery,  and  in  like  manner  the  other  "leading  wire"  from 
the  battery  is  connected  with  the  fuse  wire  of  the  hole  on 
the  extreme  right.  This  final  connection  should  not  be  made 
at  the  battery  until  all  workmen  are  at  a  safe  distance.  When 
it  is  made,  lift  the  handle  of  the  battery  and  press  it  down, 
at  first  with  moderate  speed,  but  finishing  with  full  force. 
The  leading  wires  must  be  long  enough  so  that  the  electric 
battery  is  200  to  500  ft.  away  from  the  blast,  and  in  a  di- 
rection back  of  the  face  (in  open  cut  work).  The  sun  should 
not  shine  in  the  eyes  of  the  blaster,  for  he  should  be  able  to 


134        ROCK  EXCAVATION— METHODS  AND  COST. 

see  and  dodge  any  falling  fragments  of  rock.  It  is  well  to 
wind  the  two  leading  wires  together  into  one  cable,  sepa- 
rating them  only  for  a  short  distance  from  the  blast;  then, 
after  firing,  this  cable  can  be  wound  up  on  a  reel.  As  the 
copper  connecting  wires  are  expensive,  the  blaster  should 
collect  all  fragments  of  wire  after  each  blast  and  wind  them 
upon  a  reel  to  be  spliced  and  used  again. 

Misfires. — A  misfire  when  an  electric  battery  is  used  may 
be  due  to  any  one  of  several  causes:  (i)  A  blasting  cap 
may  be  defective,  due  to  the  fact  that  water  has  penetrated 
the  cap  or  to  the  fact  that  the  platinum  bridge  in  the  cap 
has  become  unsoldered;  (2)  short-circuiting  may  be  caused 
by  a  half-hitch  taken  with  the  fuse  wire  around  the  primer 
(which  is  a  poor  but  common  practice)  which  may  have 
broken  the  insulation  so  as  to  permit  the  electric  current  to 
pass  from  one  wire  to  the  other  without  passing  through 
the  cap;  but  in  this  case  charges  in  all  other  holes  of  the 
series  will  explode;  (3)  a  defective  splice  in  the  connecting 
wires  may  have  broken  the  circuit ;(  4)  a  fuse  wire  may 
have  been  broken  in  the  process  of  tamping;  (5)  the  bat- 
tery may  be  overloaded.  This  last  cause  is  one  of  the  most 
common  causes  of  misfiring.  Any  given  battery  will  ex- 
plode a  limited  number  of  caps  in  series  through  a  given 
number  of  feet  of  copper  wire  of  given  diameter.  Increase 
the  number  of  caps,  or  increase  the  length  of  wire,  or  de- 
crease the  diameter  of  the  wire,  and  the  battery  will  fail  to 
explode  the  caps.  The  copper  of  the  leading  wires  should 
be  at  least  twice  as  thick  as  that  of  the  connecting  wires  in 
order  to  reduce  the  resistance  to  the  passage  of  the  current 
as  far  as  possible.  Never  load  a  battery  up  to  its  limit,  but 
have  a  good  margin  of  surety  that  it  will  explode  all  the 
caps  in  the  series.  Saunders  is  authority  for  the  statement 
that  a  weak  battery  may  explode  part  of  the  caps  and  leave 
the  rest  unexploded,  due  to  variations  in  the  resistance  of 
the  platinum  bridges  in  the  caps.  In  case  of  a  misfire  no 
one  should  approach  the  holes  for  half  an  hour  if  electric 


CHARGING   AND   FIRING.  135 

firing  is  used,  and  not  for  several  hours  if  fuse  firing  is  used. 
This  is  the  rule  laid  down  by  several  authorities;  but  it  is 
doubtful  whether  it  is  ever  followed  in  practice.  I  fail  to 
see  any  good  reason  for  waiting  more  than  a  few  minutes 
after  a  misfire  by  electricity ;  but  with  a  fuse  there  is  always 
danger  that  the  flame  may  smoulder  and  creep  slowly  past 
some  break  in  the  powder  thread  and  finally  explode  the  cap. 
After  waiting  some  time  it  may  be  necessary  to  remove  part 
of  the  tamping  in  the  hole  and  put  down  another  "primer." 
This  is  a  dangerous  operation  at  best,  and  if  black  powder  is 
used  a  copper  or  wooden  (never  steel)  spoon  should  be  used 
in  removing  the  tamping.  In  any  case  never  remove  the 
tamping  entirely,  but  leave  the  3  or  4  ins.  of  the  cushion 
tamping  above  the  charge  in  place.  Then  place  several  sticks 
of  dynamite  and  a  "primer"  on  top  of  the  first  charge  and 
fire  again.  The  New  York  City  rules  forbid  removing 
tamping  at  all,  and  require  that  a  new  hole  shall  be  drilled 
not  closer  than  12  ins.  to  the  old  hole,  and  that  in  this  new 
hole  a  heavy  charge  be  loaded  and  fired.  Whenever  an  ex- 
plosion fails  to  carry  away  the  rock  clear  to  the  bottom  of  a 
drill  hole  it  is  forbidden  to  begin  drilling  in  the  bottom  of 
the  old  drill  hole,  as  part  of  the  former  charge  may  remain 
unexploded  in  the  bottom  of  the  old  hole  and  explode  under 
the  blows  of  the  drill.  I  question  whether  it  is  always  safe 
practice  to  drill  a  new  hole  within  a  few  inches  of  an  old 
hole,  hoping  to  be  able  to  explode  the  charge  in  the  old  hole 
by  a  blast  in  the  new  hole.  A  safer  practice,  which  I  have 
followed  in  open-cut  work,  is  to  drill  the  new  hole  several 
feet  from  the  old  hole  and  to  a  depth  that  will  bring  the  bot- 
tom of  the  new  hole  on  a  level  with  the  top  of  the  charge 
in  the  old  hole.  Then  upon  blasting  the  new  hole  the  shat- 
tered rock  around  the  old  hole  may  be  removed,  the  dyna- 
mite exposed,  a  cap  inserted  and  fired.  Joveite  possesses  a 
decided  advantage  over  any  other  explosive  in  common  use, 
when  it  comes  to  removing  tamping  after  a  misfire  due  to  a 
poor  cap;  for  there  is  no  danger  of  exploding  it  either  by 


136        ROCK  EXCAVATION— METHODS  AND  COST. 

shock  or  by  a  spark.  Care  should  be  taken,  however,  to  use 
a  copper  or  wooden  spoon  in  removing  the  last  part  of  the 
tamping,  for  while  a  spark  will  not  explode  Joveite,  it  will 
set  fire  to  it. 

Methods  of  Firing. — Black  powder  is  exploded  by  direct 
contact  with  any  incandescent  substance,  such  as  the  burning 
train  of  powder  of  a  safety  fuse;  but  dynamite,  Judson 
powder  and  Joveite  are  exploded  only  by  detonators,  or 
"caps,"  as  they  are  commonly  called;  the  cap  in  turn  being 
exploded  either  by  a  safety  fuse  or  by  an  electric  current. 
There  is  absolutely  no  advantage  in  using  a  cap  to  explode 
black  powder,  for  it  will  not  produce  any  greater  effect. 
Black  powder  cannot  be  detonated,  but  always  explodes 
slowly. 

Safety  Fuse. — William  Bickford,  of  Cornwall,  patented 
his  justly  celebrated  safety  fuse  in  1831.  It  consists  of  a 
powder  thread  around  which  is  spun  jute  yarn,  which  is  af- 
terward waterproofed  with  coal  tar.  The  core  of  powder  is 
so  tightly  compressed  in  a  thin  thread  that  the  fire  travels 
along  it  slowly,  the  rate  in  a  good  fuse  being  I  ft.  in  1-3  to  l/2 
min.  Single  fuses  have  only  one  layer  of  waterproof  yarn 
around  the  powder;  double  fuses  have  two  layers  of  water- 
proof yarn.  Tape  fuses  are  wound  with  waterproof  tape, 
overlapping.  In  wet  holes  double  fuse  and  tape  fuse  are 
used.  For  blasting  under  water  gutta-percha  covered  fuse 
is  used. 

Caps. — A  cap  (also  called  a  blasting  cap,  a  detonator,  or 
an  exploder)  for  exploding  dynamite  consists  ordinarily  of 
a  mixture  of  mercury  fulminate  and  potassium  nitrate  or 
chlorate  placed  in  a  small  copper  capsule,  the  open  end  of 
which  is  plugged  with  sulphur,  if  the  cap  is  one  made  to  be 
fired  with  electricity ;  but  if  the  cap  is  to  be  fired  with  a  fuse 
the  fulminate  is  covered  with  shellac,  collodion,  thin  copper 
foil  or  paper,  and  the  end  of  the  capsule  is  left  open  to  re- 
ceive the  end  of  the  fuse.  Caps  for  use  with  a  fuse  are  1 1/2 
ins.  long  and  of  22  caliber. 


CHARGING   AND   FIRING.  137 

Caps  are  commonly  graded  according  to  the  amount  of 
fulminate  in  the  cap,  as  follows : 
Single  strength  (X.)  ...'....   3  grains  of  mercury  fulminate 

Double        "       (XX.) 6       "       " 

Treble         "        (XXX.)  . ...  9       "       " 
Quadruple"        (XXXX.)..i2       "       " 

And  so  on. 

There  is,  however,  no  set  rule  or  law  in  the  United  States 
as  in  England  governing  the  grading  of  caps.  In  England 
the  manufacturers  are  compelled  to  grade  their  caps  as  fol- 
lows : 

Grade    of    Cap No.  i     No.  2     No.  3     No.  4     No.  5     No.  6     No.  7     No.  8 

Charge  Fulminate  grs 4.6          6.2          8.3  10          12.3        15.4        23.1         30.9 

Fulminate  of  mercury  when  heated  to  367°  F.,  or  when 
forcibly  struck,  explodes  with  great  violence.  The  presence 
of  a  small  per  cent,  of  moisture  prevents  explosion;  hence 
caps  stored  in  a  damp  place  deteriorate  rapidly.  Mr.  W.  J. 
Orsman  has  shown  conclusively  how  quickly  caps  deteriorate 
in  a  damp  place  by  placing  a  few  caps  in  a  bottle  on  top  of 
some  damp  saw-dust.  In  24  hrs.  the  caps  had  absorbed  o.i 
per  cent,  moisture ;  in  14  days,  0.4  per  cent. ;  in  22  days,  0.5 
per  cent.  After  40  hrs.  the  caps  failed  to  explode  dynamite, 
although  they  would  still  explode  themselves.  Mr.  A.  W. 
Warwick  has  shown  *  how  important  it  is  to  use  powerful 
caps  in  exploding  dynamite  to  get  the  best  results.  To  test 
the  strength  of  caps  he  recommends  standing  a  cap  on  a  sheet 
of  lead  iy2  X  il/2  ins.  X  H  to  %  in.  thick,  enclosing  it  with 
a  pipe  and  exploding  it.  A  strong  cap  will  pulverize  the  cop- 
per shell  and  the  particles  of  the  shell  will  make  fine  marks 
in  the  lead,  around  the  deep  hole  left  where  the  cap  stood. 
A  weak  cap  will  not  pulverize  the  copper  shell,  but  will  tear 
it  into  larger  pieces,  which  make  large  marks  in  the  lead 
around  a  shallower  hole  where  the  cap  stood. 

The  stronger  the  cap  the  more  powerful  will  be  the  ex- 
plosion of  the  dynamite.  This  is  well  shown  by  the  follow- 
ing tests  made  by  Mr.  Warwick  and  published  in  Mines  and 
Minerals. 

*  Mines  and  Minerals,  Sept.  and  Oct.,  1902,  and  Feb.,   1904. 


138        ROCK  EXCAVATION— METHODS  AND  COST. 

The  dynamite  was  tested  with  the  "Abel  block."  An  "Abel 
block"  is  a  cylindrical  piece  of  lead,  5  ins.  diameter  by  5  ins. 
high,  with  a  24-in.  hole,  2l/2  ins.  deep,  in  which  a  charge  of 
5  grams  of  dynamite  is  placed  in  the  form  of  a  small  tissue 
paper  enclosed  cartridge.  The  cartridge  with  its  cap  is 
pushed  home  and  tamped  with  sand  that  has  passed  a  60- 
mesh  screen.  The  block  is  placed  between  two  i  X  6  X  6- in. 
iron  plates  and  the  whole  held  together  with  two  iron  rings, 
i^  X  i^-in.  section,  and  securely  wedged.  The  fuse  is 
fired  and  the  resulting  cavity  in  the  lead  is  measured  by  pour- 
ing in  water,  then  by  deducting  the  volume  of  the  original 
24-in.  bore  hole,  the  increased  volume  due  to  the  explosive 
is  ascertained  in  cubic  centimeters.  To  determine  the  theo- 
retical efficiency  a  simple  proportion  serves : 
35  per  cent,  powder  :  40  per  cent,  po'wder  :  :  129.3  cu.  cm.  :  141.2 

cu.  cm. 

Careful  tests  showed  not  to  exceed  4  per  cent,  variation 
in  the  effectiveness  of  samples  taken  from  different  parts  of 
the  same  commercial  stick  of  dynamite,  while  even  less  varia- 
tion wa*s  found  in  sticks  taken  from  various  parts  of  different 
boxes.  This  leads  to  the  very  important  conclusion  that  mis- 
fires in  mining  or  quarrying  cannot  be  attributed  to  lack  of 
uniformity  of  cartridges,  when  the  dynamite  is  not  frozen. 
Tests  on  two  different  makes  of  dynamite  showed  the  effec- 
tiveness of  varying  percentages  of  nitroglycerin  thus: 
30  per  cent,  dynamite  .35.3  35  per  cent,  dynamite  44.5 

40  "      "  "          43-1          40  "      "  "          47-6 

60  "  61.7          60  "      "  63.3 

These  results  show  conclusively  that  the  absorbent  dope 
of  low-grade  powders  adds  materially  to  their  effectiveness. 

Another  set  of  experiments  was  made  to  show  the  relative 
strength  of  a  given  dynamite  using  different  strength  of 
caps :  3x  cap.  4x  cap.  5x  cap. 

35  per  cent,  dynamite 37.4  40.2  44.7 

40    "  40.9  41.6  46.8 

60    "   •    "  "          59.7  62.2  63.3 


CHARGING   AND   FIRING.  139 

From  which  we  see  that  with  35  per  cent,  dynamite,  the  5x 
cap  gives  19^  per  cent,  increased  efficiency  as  compared  with 
the  3x  cap;  with  40  per  cent,  powder,  15  per  cent,  increased 
efficiency ;  60  per  cent,  powder,  not  quite  6  per  cent,  increased 
efficiency. 

As  a  further  confirmation  of  these  tests  the  running  of 
three  cross-cut  drifts  in  diabase  showed  similar  results.  The 
drilling  was  done  by  hand  hammers  with  %-in.  drills,  and  40 
per  cent,  dynamite  was  used.  The  work  was  done  in  winter 
when  the  outside  temperature  was  many  degrees  below  zero. 
The  different  caps  were  used  for  one  week  in  each  of  the 
three  drifts,  and  the  advance  carefully  measured.  The  "duty" 
of  the  dynamite  was  measured  in  cubic  feet  of  rock  loosened 
by  a  pound  of  dynamite,  and  was  as  follows : 

3x  caps.        4x  caps.         5x  caps. 
Drift  No.  i 19.4  23.5  22.8 

"     No.  2 17.6  24.2  25.1 

"     No.  3 18.7  22.6  23.7 

Average  "duty" 18.6  23.4  23.8 

Cost  per  ft.  of  drift $6.34  $5-75  $5-72 

As  a  result  of  these  tests,  5x  caps  were  used  in  winter  and 
4x  caps  in  summer.  When  the  3x  caps  were  used  the  dyna- 
mite fumes  were  so  bad  as  to  make  it  impossible  for  the  men 
to  work  well.  Caps  should  always  be  stored  in  a  dry  atmos- 
phere; keeping  them  long  underground  is  apt  to  weaken 
them  materially. 


Fig.  12. 


Electric  Detonators. — The  electric  detonator  or  "platinum 
fuse,"  as  it  is  called  by  some  makers,  has  a  composition  sim- 
ilar to  the  fuse  cap  described  in  the  previous  paragraph,  and 
all  that  is  there  given  regarding  strength  and  use  of  caps  ap- 
plies to  the  electric  cap,  or  "fuse."  Fig.  12  shows  an  electric 


140        ROCK  EXCAVATION— METHODS  AND  COST. 

cap  in  which  A  is  the  copper  shell ;  B  the  fulminate  of  mer- 
cury ;  C  the  insulated  copper  fuse  wires ;  D  the  bare  ends  of 
the  fuse  wires  projecting  through  the  sulphur  plug,  F;  E 
the  platinum  wire  called  the  "bridge"  soldered  to  the  fuse 
wires.  This  platinum  "bridge"  is  heated  red  hot  when  the 
electric  current  passes  through  the  wires,  and  thus  explodes 
the  fulminate  of  mercury.  The  fuse  wires,  C,  are  4  ft.  to 
30  ft.  long,  depending  upon  the  depth  of  the  blast  hole.  They 
are  insulated  with  cotton.  The  ends  of  these  fuse  wires  are 
connected  to  "connecting  wires"  that  reach  from  hole  to  hole. 
The  sulphur  plug  does  not  make  detonators  entirely  water- 
proof, for  the  copper  of  the  shell  expands  more  than  the 
sulphur  upon  any  rise  of  temperature  in  the  air,  and  thus 
opens  a  slight  crack  through  which  moisture  may  reach  the 
fulminate  of  mercury.  Shoemakers'  wax,  warmed,  then 
cooled  until  jelly  like,  if  daubed  around  the  end  of  the  ex- 
ploder, will  keep  out  water  when  using  exploders  in  wet 
holes.  Tallow  may  also  be  used,  but  is  not  so  effective.  In 
nine  cases  out  of  ten,  failure  to  explode  a  series  of  holes  by 
electricity  is  due  to  a  defective  exploder.  The  cause  may  be 
moisture  that  has  reached  the  mercury  fulminate  while  the 
caps  were  stored  or  after  charging  in  the  hole ;  or  it  may  be 
that  the  platinum  bridge  has  broken  from  the  copper  fuse 
wires.  Care  should  be  taken  never  to  pull  hard  upon  the  fuse 
wires,  for  fear  of  loosening  the  platinum  bridge. 


CHAPTER  IX. 
METHODS  OF  BLASTING. 

The  Theory  of  Blasting. — The  rules  commonly  found  in 
text  books  are  based  upon  theories  which  in  turn  are  founded 
upon  assumptions  as  to  conditions  not  often  encountered  in 
practice.  One  may  safely  look  with  suspicion  upon  any  dog- 
matic rule  as  the  amount  of  explosive  to  use  and  the  spacing 
of  blasting  holes.  In  the  first  place  most  of  the  "rules  for 
blasting"  were  originated  by  users  of  black  powder,  and  are 
valueless  when  applied  to  high  power  explosives.  In  the 
second  place,  many  of  the  rules  apply  only  to  single  shots, 
and  not  to  the  simultaneous  firing  of  many  holes  by  elec- 
tricity. In  the  third  place,  practically  all  of  the  rules  ignore 
the  use  to  which  the  blasted  rock  is  to  be  put.  The  last  is 
perhaps  the  most  conclusive  reason  why  "rules  for  blasting," 
no  matter  how  high  the  authority  back  of  them,  are  apt  to 
be  exceedingly  misleading. 

Rock  that  is  quarried  for  dimension  stone  masonry  re- 
quires close  spacing  of  blast  holes  on  a  straight  line,  but  these 
rows  of  holes  themselves  may  be  several  feet  apart.  When 
holes  are  drilled  close  together  in  this  way  and  fired  simul- 
taneously, using  very  small  charges  of  black  powder  in  each 
hole,  a  huge  block  of  solid  rock  may  be  wedged  off  without 
shattering  it. 

Rock  that  is  quarried  for  concrete  or  macadam  purposes 
should  be  well  shattered  to  save,  the  cost  of  sledging  and 
"blockholing"  into  sizes  that  will  enter  the  crusher.  This 
means  an  entirely  different  spacing  of  the  holes  from  di- 
mension stone  quarrying,  and  it  usually  means  the  use  of  a 
high  power  explosive  that  will  thoroughly  shatter  the  rock. 

In  the  two  cases  just  cited  the  rock  is  put  to  some  use  after 
it  is  quarried ;  but  in  open-cut  work  on  canals  and  railways 
the  rock  is  frequently  wasted,  and  is  broken  up  only  to  as 

141 


142        ROCK  EXCAVATION— METHODS  AND  COST. 

small  sizes  as  can  be  handled  conveniently  by  the  appli- 
ances available.  In  some  cases  these  appliances  are  simply 
crowbars  for  levers  and  boards,  for  inclined  planes,  up 
which  the  stone  may  be  rolled  by  hand  into  wagons.  In  other 
cases  derricks  that  can  lift  only  a  ton  or  so  are  available; 
while  in  still  other  cases  cableways  that  can  handle  a  mass 
of  ten  tons  are  to  be  used ;  or  it  may  happen  that  steam  shov- 
els are  to  load  the  stone,  in  which  case  it  must  be  shattered 
to  comparatively  small  sizes. 

With  all  these  variable  factors,  how  absurd  it  is  to  la) 
down  any  inflexible  "rules  for  blasting,"  and  yet  we  find 
such  rules  in  every  text  book.  Often,  it  is  true,  the  author 
forewarns  us  that  judgment  must  be  used  in  applying  the 
rules,  but  neglects  to  tell  us  afterward  where  and  how  to  ac- 
quire that  judgment.  Indeed,  by  the  very  act  of  omitting 
to  say  anything  further  as  to  the  exercise  of  judgment,  the 
author  permits  us  to  forget  that  he  has  told  us  that  the  rules 
must  be  used  with  judgment.  I  cannot  hope  to  be  able  to 
explain  how  blasting  should  be  done  in  every  case,  but  I  hope 
to  keep  constantly  before  the  reader  the  desirability  of 
reasoning,  instead  of  persuing  the  much  easier,  but  in  the 
end  the  more  costly,  practice  of  following  "rules." 

The  Crater  Theory. — Regarding  the  theory  of  blasting, 
much  more  has  been  put  into  print  than  is  warranted  by  the 
meagre  scientific  experiments  made  by  the  writers.  A  com- 
monly quoted  theory  of  the  action  of  an  explosive  is  one  that 
may  be  termed  "the  crater  theory."  According  to  this  theory 
an  explosive  buried  in  a  mass  of  earth  or  rock  will  blow  out 
a  funnel-shaped  crater  whose  sides  are  supposed  to  have  a 
slope  of  i  to  i,  if  the  surface  of  the  earth  or  rock  is  hori- 
zontal, as  shown  in  Fig.  13.  The  distance  D  B;  or,  to  be 
more  exact,  the  distance  D  F  from  the  surface  of  the  rock 
or  earth  to  the  center  of  the  charge  of  powder,  E  B,  is  called 
the  "line  of  least  resistance."  The  volume  of  the  funnel  or 
crater  is : 

V=  Jl  x  wl2  =  I3  (nearly) 


METHODS  OF  BLASTING. 


143 


Hence  the  general  formula  for  the  volume  of  rock  loosened 
by  one  charge  so  as  to  form  a  funnel  crater  is : 

V  =  ml3 

According  to  Schoen,  m  =  0.4  for  tough,  soft  rock, 
m  =  0.9  for  hard,  brittle  rock. 

This  means  that  in  tough  soft  rock  the  sides  of  the  crater 
are  steeper  than  i  to  I,  but  in  hard,  brittle  rock  they  are 
nearly  I  to  I. 

Note  carefully  that  this  theory  assumes  two  things ;  first, 
that  only  one  charge  of  explosive  is  fired  at  a  time ;  second, 
that  the  rock  is  homogenous  and  has  no  seams  or  cracks. 
Except  for  chamber  blasting,  this  theory,  in  my  opinion,  is 
not  worth  the  ink  it  is  printed  with;  because,  in  practice, 
shots  are  not  fired  singly  nor  is  the  rock  ordinarily  free  from 
seams  and  joints. 

If  the  drill  holes  were  bored  vertically  in  rock,  as  in  Fig. 
13,  and  heavily  charged  with  black  powder,  it  might  blow 
out  the  tamping  and  fail  to  rupture  the  rock  at  all.  The  writ- 
ers who  have  accepted  the  "crater  theory"  have,  therefore, 
reasoned  that  drill  holes  should  be  drilled  at  an  angle  with 
the  surface,  along  some  such  line  as  A  B,  instead  of  along 
the  line  of  least  resistance,  D  B,  as  shown  in  Fig.  13.  If 


H 


K---I' H 


Fig.  14. 

this  were  done  the  length  of  the  line  of  "least  resistance," 
D  B,  would  be  about  0.7,  or  nearly  y%  the  length  of  the  drill 
hole  A  B.  Hence  we  find  the  rule  laid  down  with  the  ut- 
most dogmatism,  that  "the  line  of  least  resistance  should 
never  be  more  than  three-quarters  the  length  of  the  drill 


144        ROCK  EXCAVATION— METHODS  AND  COST. 

hole."  Then  they  go  a  step  further  and  show  us  a  drill  hole 
in  a  bench,  as  in  Fig.  14,  placed  back  from  the  face  so  that 
the  distance  from  the  face  is  three-quarters  the  depth  of  the 
hole,  and  they  tell  us  that  this  ratio  should  never  be  exceeded. 
With  single  shots,  with  black  powder,  with  a  rock  perfectly 
homogeneous,  we  may  concede  that  there  is  some  reason  in 
this  rule,  but  as  it  is  given  in  text  books  without  any  qualifi- 
cations or  explanations  at  all,  the  rule  is  worthless.  With 
dynamite  I  have  often  placed  a  row  of  holes  a  distance  back 
from  the  face  just  twice  as  much  as  this  rule  permits;  and 
the  result  has  been  excellent  when  the  rock  was  much  seamed 
and  easily  broken  by  holes  fired  simultaneously. 

The  advocates  of  the  crater  theory  of  blasting  recommend 
that  the  "rock  coefficient"  be  obtained  for  any  given  kind 
of  rock  as  follows :  Drill  a  row  of  holes  2  ft.  back  from  the 
vertical  face  of  rock  to  be  blasted  down  in  benches.  Let 
these  vertical  holes  be  6  ft.  apart  and  3  ft.  deep.  Charge  one 
hole  with  a  very  small  charge  of  explosive ;  charge  the  next 
hole  with  a  greater  charge ;  and  so  on,  charging  each  hole 
heavier  than  the  last.  Tamp  and  fire  the  holes  separately, 
and  select  that  hole  which  has  given  the  best  results — the 
one  that  has  broken  rock  without  hurling  it  far.  Suppose 
this  particular  hole  was  charged  with  0.5  Ib.  of  dynamite, 
then  the  "rock  coefficient"  is : 

o  5    o.  c 

^f=ir=0-06 

The  rule  is :  Divide  the  charge  of  the  explosive  in  pounds 
by  the  cube  of  the  line  of  least  resistance  in  feet  to  get  the 
"rock  coefficient."  Then,  they  tell  us,  we  have  only  to  mul- 
tiply this  "rock  coefficient"  by  the  cube  of  the  line  of  least 
resistance  that  we  intend  to  use  in  practice,  to  ascertain  the 
proper  charge  for  each  hole.  Thus,  if  we  are  going  to  drill 
holes  so  that  the  line  of  least  resistance  will  be  8  ft.,  we  mul- 
tiply 0.06  by  83,  or  0.06  X  8  X  8  X8,  and  we  get  30.72  Ibs. 
as  the  proper  charge  per  hole.  I  have  tested  this  rule,  and, 
as  I  had  anticipated,  I  have  found  that  it  gives  too  large  a 


METHODS  OF  BLASTING.  145 

charge  for  deep  holes  in  stratified  rock  with  a  long  line  of 
least  resistance. 

Wherein  is  the  "crater  theory"  defective?  To  begin  with 
it  assumes  that  the  work  the  powder  has  to  do  is  en- 
tirely dependent  upon  the  volume,  or  weight,  of  rock  to  be 
moved ;  that  if  0.8  Ib.  of  powder  will  break  I  cu.  yd.  of  rock 
in  a  shallow  hole,  the  same  proportion  of  powder  will  break 
the  rock  in  precisely  the  same  manner  in  a  deep  hole,  re- 
quiring always  the  same  fraction  of  a  pound  of  powder  per 
cu.  yd.  whether  the  holes  are  deep  or  shallow.  Every  ex- 
perienced blaster  knows  that  this  is  not  so.  Generally  the 
deeper  the  holes  (and  consequently  the  longer  the  line  of 
least  resistance)  the  less  the  number  of  pounds  of  powder 
required  per  cubic  yard.  We  have,  therefore,  a  reductio  ad 
absurdum  so  far  as  the  crater  theory  is  concerned.  More- 
over, when  we  consider  the  work  that  an  explosive  has  to  do, 
we  find  no  good  reason  for  assuming  that  equal  weights  of 
powder  will  break  equal  weights  of  rock  regardless  of  depth 
of  holes.  The  force  of  the  powder  is  expended  in  four  ways : 
(i)  shearing  the  rock  loose;  (2)  in  overcoming  the  inertia 
of  the  rock  mass;  (3)  in  heating  the  rock;  and  (4)  in  im- 
parting motion  to  the  surrounding  air.  If  all  the  work  were 
expended  in  shearing  the  rock,  then  since  the  volume  of  a 
crater  varies  as  the  cube  of  the  line  of  least  resistance,  while 
the  area  of  the  slopes  of  the  crater  varies  as  the  square  of 
the  line  of  least  resistance,  it  is  evident  that  the  shorter  the 
line  of  least  resistance  the  greater  the  unit  work  done  by  the 
powder  in  shearing  loose  the  rock.  Thus  a  crater  2  ft.  deep, 
having  an  apex  angle  of  90°,  has  an  area  of  side  slopes  of 
35.4  sq.  ft.  and  a  volume  of  8.4  cu.  ^d/.7or  4.2  sq.  ft.  per  cu. 
ft.  A  crater  8  ft.  deep  has  an  area  of  567  sq.  ft.  and  a  volume 
of  536  cu.  ft,  or  i. 06  sq.  ft.  per  cu.  ft.  Hence  the  work  of 
shearing  off  the  rock  in  the  8-ft.  crater  is  about  one-fourth 
as  much  per  cu.  yd.  as  the  corresponding  work  in  the  2-ft. 
crater.  In  a  well-charged  blast,  where  the  rock  is  merely 
shattered,  but  not  heaved,  the  work  of  overcoming  the  inertia 


146        ROCK  EXCAVATION— METHODS  AND  COST. 

of  the  rock  is  comparatively  slight;  but  we  do  not  know, 
and  can  at  present  not  even  guess,  what  portion  of  the  energy 
of  the  powder  is  entirely  lost  in  heating  the  rock  and  in  im- 
parting motion  to  the  air.  For  all  that  can  now  be  proved 
to  the  contrary,  we  might  assume  that  this  percentage  of  lost 
work  is  a  constant  percentage  in  large  and  in  small  blasts.  If 
so,  the  crater  theory  crumbles  at  once  into  meaningless 
words ;  if  not  so,  the  advocates  of  the  crater  theory  still  have 
to  prove  that  their  primary  assumptions  are  based  upon  rea- 
sons having  even  the  semblance  of  scientific  truth.  I  have 
a  great  respect  for  any  one  who  formulates  a  theory  that  ac- 
cords with  experience;  but  I  have  no  respect  for  a  theory 
that  utterly  fails  to  help  the  practical  man  and  actually  mis- 
leads him,  as  exemplified  in  the  crater  theory  of  blasting. 

Placing  Drill  Holes. — In  the  days  of  black  powder  it  was 
essential  to  consider  carefully  the  position  of  seams  and  bed- 
ding planes  in  the  rock  so  as  to  place  the  drill  hole  where  the 
powder  would  have  the  least  possible  work  to  perform  in 
shearing  off  the  rock.  Upon,  the  introduction  of  dynamite  it 
was  found  that  less  care  need  be  taken  in  placing  the  drill 
holes  with  regard  to  natural  seams  in  the  rock,  excepting  in 
quarrying  dimension  stone.  Nevertheless,  some  attention 
should  always  be  given  to  the  position  of  planes  of  weak- 
ness, especially  in  stratified  rock.  In  open-cut  work,  where 
the  rock  is  excavated  in  benches,  it  is  well  to  have  the  bot- 
tom of  the  drill  hole  stop  just  short  of  a  plane  of  stratifica- 
tion or  weakness  in  the  rock,  even  if  to  do  so  necessitates 
drilling  holes  somewhat  shallower  than  they  would  be  drilled 
in  rock  uniformly  solid.  In  tunneling  and  shaft  sinking, 
where  hand  drills  are  used,  care  is  always  taken  to  locate  the 
"cut  holes"  with  reference  to  seams  or  planes  of  weakness 
in  the  rock.  If  the  strata  in  a  hand-driven  tunnel  dip  down- 
ward toward  the  face,  drill  and  fire  the  first  holes  near  the 
roof;  if  the  strata  dip  down  away  from  the  face,  drill  and 
fire  the  first  holes  near  the  floor.  In  any  case  drill  a  hand- 
driven  hole  as  nearly  perpendicular  as  possible  to  the  planes 


METHODS  OF  BLASTING.  14? 

of  weakness  in  the  rock.  The  spacing  of  holes  will  be  given 
in  subsequent  chapters. 

Springing  Holes. — In  order  to  enlarge  a  drill  hole  so  that 
a  greater  charge  of  powder  may  be  placed  in  the  hole,  a  few 
sticks  of  dynamite  may  be  exploded  at  the  bottom  of  the  hole 
so  as  to  make  a  chamber  there.  This  process  is  variously 
termed  "chambering,"  "springing,"  "shaking,"  "bullying," 
etc.  In  earth  and  soft  rocks  like  shale,  the  dynamite  used 
in  springing  the  hole  compresses  the  material  at  the  bottom 
of  the  hole  and  thus  enlarges  the  hole ;  in  hard  rock  the  dyna- 
mite pulverizes  some  of  the  rock  and  hurls  the  powdered 
rock  out  into  the  air,  leaving  a  chamber.  In  very  soft  ma- 
terial the  first  springing  will  make  a  sufficiently  large  cham- 
ber; but  in  hard  rock  repeated  springing,  with  increasingly 
large  charges  of  dynamite,  becomes  necessary.  Thus  in 
springing  2o-ft.  holes  in  sandstone  I  have  used  for  the  first 
springing  shot  2  sticks  of  40  per  cent,  dynamite;  for  the 
second  springing  shot,  5  sticks ;  for  the  third  shot,  20  sticks. 
The  chamber  thus  made  was  charged  with  8  kegs,  or  200  Ibs. 
of  black  powder. 

Springing  can  be  used  with  great  ecohomy  of  explosives 
in  open-cut  work  where  deep  holes  can  be  thus  enlarged  and 
charged  with  black  powder  or  Judson  powder.  It  is  indeed 
surprising  to  note  how  often  holes  are  charged  with  dyna- 
mite and  fired  without  any  attempt  to  test  the  springing 
method  of  blasting.  On  the  other  hand,  I  have  frequently 
seen  the  springing  method  used  under  conditions  not  at  all 
favorable;  thus  in  6- ft.  holes  in  hard  limestone,  where  a 
sewer  trench  was  being  excavated,  the  contractor  was  firing 
in  successive  shots  a  total  of  8  or  10  sticks  of  dynamite  for 
the  sake  of  crowding  a  few  more  sticks  into  the  bottom  of 
the  hole  for  the  final  shot.  A  much  more  economic  arrange- 
ment of  powder  in  sewer  trenches  is  to  distribute  it  in  small, 
separate  charges  from  the  bottom  to  near  the  top  of  hole, 
and  not  to  concentrate  it  at  the  bottom.  In  tunneling,  on  the 
•other  hand,  it  is  always  desirable  to  concentrate  as  much  of 


148        ROCK  EXCAVATION— METHODS  AND  COST. 

the  charge  as  possible  at  the  bottom  of  the  hole ;  and,  were  it 
not  for  the  fumes  and  dust  produced  by  springing,  it  would 
always  be  good  practice  in  railway  tunneling  through  com- 
paratively soft  rock  to  spring-  the  holes.  With  water  for 
spraying  the  air  after  each  shot  the  objection  to  springing 
the  holes  would  disappear.  In  stoping,  shaft  sinking  and 
tunneling^  there  is  every  reason  for  concentrating  the  charge 
as  much  as  possible  at  the  bottom  of  the  hole,  and  no  pains 
should  be  spared  in  experimenting  with  the  springing  method 
of  blasting,  even  to  the  installation  of  a  water  supply  system 
for  clearing  the  air  of  dust  and  fumes  after  each  springing 
shot.  In  open-cut  work  it  is  not  so  essential  to  have  the 
charge  in  the  bottom  of  the  hole  if  dynamite  or  Joveite  is 
used ;  but  if  black  powder  or  Judson  powder  is  to  be  used  a 
sufficient  quantity  cannot  be  charged  in  the  hole  of  ordinary 
diameter  unless  the  holes  are  placed  close  together.  The 
use  of  the  springing  method  enables  the  blaster  to  place  the 
holes  far  apart  in  stratified  rocks  (and  thus  reduce  the  cost 
of  drilling),  and  to  load  them  with  large  charges  of  low- 
grade  powder,  thus  reducing  both  the  cost  of  drilling  and  of 
explosive. 

In  springing  a  deep  hole  it  is  customary  to  tamp  the 
springing  shot  with  a  small  quantity  of  sand,  no  attempt 
being  made  to  fill  the  hole  with  tamping.  In  shallow  holes 
in  mines  and  tunnels  less  than  a  stick  of  75  per  cent,  dyna- 
mite, well  packed,  may  be  used  for  the  first  springing  shot, 
lowering  or  shoving  into  the  hole  a  small  "primer"  contain- 
ing the  cap ;  tamp  with  fine  sand,  and  fire. 

After  the  hole  has  been  sprung,  if  it  is  to  be  loaded  with 
black  powder,  care  should  be  taken  not  to  put  the  powder 
in  before  the  rock  has  cooled  off.  It  sometimes  happens  that 
the  chamber  made  by  springing  is  not  large  enough  to  hold 
the  necessary  charge  of  powder ;  in  such,  cases  there  is  an 
advantage  where  Judson  powder  has  been  used,  for  the  Jud- 
son powder  may  be  ignited  and  will  burn  up  without  explod- 
ing, thus  making  it  possible  to  enlarge  the  hole  by  further 


METHODS  OF  BLASTING. 


149 


springing.  Where  the  rock  strata  are  inclined  at  a  high 
angle  it  sometimes  happens  that  the  shock  of  springing  will 
cause  a  slip,  closing  up  the  chamber  and  causing  a  loss  of  the 
hole. 

Blasting  with  Powder  and  Dynamite  Together. — In  blast- 
ing blue  sandstone  on  the  Wabash  Railroad  in  eastern  Ohio, 
Mr.  W.  M.  Douglass,  of  Douglass  Bros.,  has  found  that  the 
most  effective  way  of  blasting  so  as  to  reduce  the  stone  to 
small  sizes  easily  handled  by  a  steam  shovel  is  to  fire  large 
charges  of  black  powder  and  dynamite  in  alternate  rows  of 
holes.  *  Figs  15  and  16  show  two  typical  blasts,  Fig.  16 

Line  of  Bcrck  Break 

West  Face 


*z> 

^<k--/7-'-. 


!  ~      ,    -iT 

' 17'- -*"¥-• 


.....  17' 


17' 


** 


17- 


, 
.....  17  ------- 


h--~ 34'-- ->t 

East  Face 


Face  of  Cut,  East 

Fig.  15.  Fig.  16. 

being  the  last  blast  fired  when  there  were  two  faces.  The 
holes  were  all  drilled  24  ft.  deep  with  a  well  driller,  the  bit 
being  3  ins.  in  diameter  at  the  bottom  of  the  hole.  The  holes 


*  See  page  92  for  the  cost  of  drilling  in  this  sandstone. 


150        ROCK  EXCAVATION— METHODS  AND  COST. 

marked  "kegs"  were  loaded  with  the  number  of  25-lb.  kegs 
of  black  powder  given  in  the  diagrams,  after  springing  with 
dynamite.  In  springing  each  hole  in  Fig.  16,  15  sticks  (ij4  x 
8-in.  size)  were  first  fired,  then  40  sticks,  then  80  sticks  and 
finally  130  sticks,  a  total  of  265  sticks,  or  about  132  Ibs.  of  40 
per  cent,  dynamite  per  hole  for  springing.  The  holes  marked 
"boxes"  were  loaded  straight  (without  springing)  to  within 
4  ft.  of  the  top,  each  hole  containing  as  many  5O-lb.  boxes  of 
40  per  cent,  as  indicated  by  the  figures  in  the  diagrams.  In 
making  a  blast  the  dynamite  and  black  powder  were  fired 
together,  the  theory  being  that  the  black  powder  would  lift 
the  rock,  while  the  dynamite  would  shatter  it.  The 
results  were  excellent.  The  blast  shown  in  Fig. 
15  broke  the  rock  up  for  20  ft.  back  of  the  last 
row  of  holes;  and,  in  making  this  blast,  about  800  Ibs. 
of  dynamite  were  used  in  springing  the  six  holes,  beside  the 
1,100  Ibs.  of  dynamite  used  in  the  blast  itself ;  6,000  Ibs.  of 
black  powder  were  also  used  in  this  blast.  The  amount  of 
rock  within  the  boundary  lines  of  the  outer  holes,  to  a  depth 
of  24  ft.,  was  about  2,100  cu.  yds. ;  and  it  was  2,700  cu.  yds. 
within  the  boundary  lines  of  the  diagram  back  to  the  "line 
of  back  break."  For  the  blast  shown  in  Fig.  16  there  were 
used  i, 600  Ibs.  of  dynamite  in  springing  the  holes,  1,000  Ibs. 
of  dynamite  in  the  blast  and  9,425  Ibs.  of  black  powder  in 
the  blast.  The  amount  of  rock  within  the  boundary  lines  of 
the  diagram  (to  depth  of  24  ft.)  was  more  than  2,400  cu. 
yds.  The  rock  was  excavated  for  2  or  3  ft.  outside  the 
boundary'  lines. 

Large  Chamber  Blasts. — We  have  seen  how  by  springing  a 
drill  hole  a  small  chamber  can  be  made  so  as  to  receive  a  com- 
paratively large  charge  of  explosive,  and  thus  reduce  the 
number  of  feet  of  drill  hole  per  cubic  yard  of  rock  thrown 
down.  This  method  may  be  carried  out  on  a  much  larger 
scale  by  driving  a  small  tunnel  or  sinking  a  shaft  at  the  end 
of  which  chambers  are  prepared  to  receive  a  great  charge  of 
explosive.  In  this  way  a  mountain  of  rock  .may  be  broken 


METHODS  OF  BLASTING.  151 

down  at  one  shot,  with  a  great  saving  in  labor  and  powder. 
This  method  of  chamber  blasting  is  particularly  economic  in 
breaking  down  banks  of  hardpan  for  removal  either  by  steam 
shovels  or  by  hydraulicking.  Unfortunately  there  is  not  a 
great  deal  in  print  relative  to  chamber  blasting,  but  by  search- 
ing I  have  found  enough  to  give  a  good  idea  of  the  methods 
and  an  approximate  idea  of  the  size  of  charges  used.  Writ- 
ers without  exception  fail  to  state  how  much  "block  holing" 
was  necessary  to  reduce  the  chamber-blasted  rock  to  sizes 
that  can  be  handled  by  derricks  or  that  will  pass  through 
crushers. 

The  following  abstracts  of  articles  on  chamber  blasting 
contain  valuable  information : 

In  Engineering  News,  May  17,  1900,  "W.  M."  describes 
"the  second  largest  blast  in  the  history  of  high  explosives," 
fired  Dec.  18,  1899,  at  West  Beaver  Creek,  Col.,  by  the  Pike's 
Peak  Power  Co.,  for  the  building  of  a  rock-fill  dam  requir- 


Fig.  17. 

ing  42,000  cu.  yds.  of  rock.  A  granite  "butte"  or  cone  of 
rock  was  selected  and  a  tunnel  run  into  it  75  ft.  below  its 
apex.  The  tunnel  was  135  ft.  long,  and  had  several  bends 
in  it,  Fig.  17,  so  as  to  render  blowing  out  of  the  charge  im- 
possible. Cross  drifts  were  run  35  ft.  each  way  from  the 
end  of  the  tunnel.  In  these  cross  drifts  were  charged  32,000 
Ibs.  of  black  powder  and  144  Ibs.  of  dynamite,  distributed  as 


152        ROCK  EXCAVATION— METHODS  AND  COST. 

shown,  and  packed  solid  with  bulkheads,  b,  of  sacks  of 
powder.  The  remaining  part  of  the  T  was  filled  with  rock 
and  earth,  except  along  one  wall  where  3,000  Ibs.  of  powder 
were  placed  in  bags,  E.  Firing  holes,  d,  36  in  number  and  5 
ft.  deep,  containing  4  Ibs.  of  dynamite  each,  with  3  electric 
exploders  each,  were  connected  in  series,  making  three  cir- 
cuits, so  that  in  case  one  circuit  was  found  to  be  open 
another  would  be  available.  The  main  tunnel  was  tamped 
solid  with  rock  and  earth,  timber  bulkheads  being  placed  at  c. 
The  firing  station  was  3,000  ft.  away.  The  explosion  opened 
a  crater  72  ft.  deep  and  150  ft.  wide,  breaking  110,000  cu. 
yds.  of  rock,  or  80  per  cent,  of  the  rock  above  the  tunnel 
level.  A  tunnel  through  the  rim  of  the  crater  gave  access 
to  the  broken  rock.  Mr.  R.  M.  Jones  was  the  engineer  of  the 
company. 

Mr.  W.  R.  Russel  is  authority  for  the  following  data  on 
chamber  blasting  for  a  rock-fill  dam  at  Otay,  Cal. :  The 
rock  was  a  porphyry,  easily  broken,  but  very  hard  to  drill. 
Quarrying  was  begun  by  drilling  holes  by  hand  12  to  20  ft. 
deep,  but  this  was  found  to  be  too  slow  and  expensive,  so  it 
was  decided  to  run  a  tunnel  and  make  one  large  blast.  This 
was  done  by  driving  a  4  x  55^-ft.  drift  50  ft.  and  then  branch- 
ing so  as  to  form  a  Y.  The  drift  was  large  enough  so  that 
double-hand  drilling  could  be  used.  The  ends  of  the  Y  were 
enlarged  to  form  powder  chambers.  The  chamber  on  the 
right  held  4,000  Ibs.  of  Judson  powder;  the  one  on  the  left 
held  8,000  Ibs.  A  5O-lb.  box  of  dynamite  was  placed  in 
each  chamber.  The  drift  was  completely  packed  with  earth 
and  sand.  This  blast  threw  down  about  50,000  cu.  yds.  of 
rock,  at  a  cost  of  3.6  cts.  per  cu.  yd.  The  cost  was : 

86-ft.   drift    $645 

12,000  Ibs.  Judson 960 

Charging     75       • 


Total    $1,680 


METHODS  OF  BLASTING.  153 

Part  of  these  50,000  cu.  yds.  was  further  broken  up  by 
firing  powder  in  the  seams,  making  a  total  cost  of  5  cts.  per 
cu.  yd. 

For  the  second  blast  a  shaft  was  sunk  to  a  depth  of  115  ft. 
and  about  85  ft.  back  from  the  quarry  face.  At  a  depth  of 
50  ft.  two  drifts  were  run  in  opposite  directions  for  25  ft., 
and  a  powder  chamber  was  made  at  each  end.  At  the  bot- 
tom of  the  shaft  two  more  drifts  were  run,  one  35  ft.,  the 
other  30  ft.  The  total  charge  was  15  tons  of  powder,  the 
greater  part  being  in  the  bottom  chambers.  This  blast  was 
also  very  satisfactory.  In  both  cases  the  electric  wires  were 
laid  in  i-in.  pipes,  which  were  covered  by  the  sand  tamp- 
ing, and  the  tamping  was  moistened  to  make  it  more  effec- 
tive. After  these  large  blasts  there  was  never  any  stopping 
of  work  to  fire,  for  the  larger  rocks  were  block  holed  and 
blasted  at  noon  and  at  night.  A  derrick  delivered  the  rock 
to  a  Lidgerwood  cableway  of  955  ft.  span,  capable  of  han- 
dling a  lo-ton  load.  As  high  as  250  skip  loads  were  handled 
in  10  hrs.,  the  daily  average  being  200  loads.  The  time 
consumed  in  hoisting  and  lowering  a  skip  was  20  per  cent, 
of  the  time  required  to  make  the  trip  from  the  quarry  to  the 
dam. 

A  large  blast  was  fired  March  3,  1898,  by  Carpenter  Bros, 
to  blow  down  an  isolated  mass  of  trap  rock  known  as  "In- 
dian Head,"  near  Fort  Washington  on  the  Hudson  River. 
Two  tunnels  were  driven ;  one  near  the  water  edge  and  65 
ft.  deep ;  the  other  about  60  ft.  from  the  top  and  80  ft.  deep. 
The  face  was  200  ft.  high.  Two  25-ft.  shafts  were  sunk 
from  the  upper  tunnel,  and  drill  holes  besides.  A  charge  of 
3,000  Ibs.  of  dynamite  was  placed  in  one  tunnel,  and  4,000 
Ibs.  in  the  other ;  and  it  was  estimated  that  with  the  7,000 
Ibs.  there  were  350,000  tons  of  trap  rock  thrown  down. 

Mr.  O.  Guttmann,  in  a  paper  read  before  the  Inst.  of  C.  E., 
gives  data  on  chamber  blasting  on  the  Danube  River.  A 
spur  of  rock  had  a  vertical  face  toward  the  river.  A  head- 
ing 3  ft.  wide  by  4  ft.  high  was  driven  in  straight,  and  then 


154        ROCK  EXCAVATION— METHODS  AND  COST. 

a  chamber  6  x  6  x  6  ft.  made  at  right  angles  to  it.  The 
chamber  was  charged  and  the  heading  closed  by  brick  set  in 
cement  and  by  dry  stone  packing.  At  first  carboazotine  was 
used,  consisting  of  74  per  cent,  potassium  nitrate,  12  per 
cent,  sulphur,  8  per  cent,  soot  and  6  per  cent.  bran.  It  was 
a  low-grade  explosive ;  but,  in  one  blast  of  3.9  tons,  25,900 
cu.  yds.  were  thrown  down  where  the  breast  was  60  ft.  and 
the  height  99  ft.  The  largest  blast  was  in  May,  1894,  when 
12  tons  of  second-grade  dynamite  (containing  45  per  cent, 
blasting  gelatine)  in  two  chambers  threw  down  3  cu.  yds. 
of  rock  for  each  pound  of  explosive,  or  practically  the  same 
as  the  carboazotine. 

The  formula  used  for  charging  the  chambers  was :  L  =  3 
(v3  -f-  5h)  q.  In  this  L  is  the  weight  of  charge  in  kilo- 
grams* ;  v  the  line  of  latest  resistance  in  meters ;  h  the  height 
in  meters  of  rock  above,  and  q  a  coefficient  depending  on 
the  explosive,  being  0.22  for  carboazotine.  The  term  5h 
may  be  dropped  without  sensible  error.  The  formula  then 
is  almost  identical  with  the  formula:  L  =  4.19  r3  c,  used  in 
harbor  work  at  Fiume,  where  the  ratio  of  height  to  line  of 
least  resistance  was  kept  3 :  2.  Both  these  formulas  give  too 
high  a  charge,  according  to  Guttmann. 

Mr.  J.  A.  Wilson,  in  a  paper  before  the  Inst.  of  C.  E., 
gives  data  on  large  blasts  in  New  Zealand  for  harbor  works. 
The  stone  was  granite,  gneiss  and  limestone  used  in  large 
blocks.  On  an  average  i  Ib.  of  dynamite  dislodged  10  tons 
of  stone.  Separate  charges  were  proportioned  in  the  ratio 
of  the  cube  of  the  least  resistance,  and  this  cube  of  the  line 
of  resistance  was  divided  by  35  for  dynamite,  36  for  geleg- 
nite,  43  for  gelatine  dynamite,  50  for  blasting  gelatine  and 
12  for  black  powder.  Charges  of  l/\.  to  i]/2  tons  were  found 
most  effective  (a  3-ton  charge  broke  up  the  rock  too  much)  ; 
but  this  kind  of  blasting  requires  a  line  of  least  resistance 
of  less  than  40  ft.  One  or  more  free  ends  in  the  quarry  with 
a  vertical  face  are  preferable.  The  length  of  adit  was  made 

*  Kilogram  is  equal  to  2.2  Ibs, 


METHODS  OF  BLASTING.  155 

nearly  half  the  height  overhead,  and  the  chambers  were  a 
distance  apart  equal  to  15  times  the  line  of  least  resistance. 
In  Engineering  News,  April  2,  1892,  large  blast  firing  at 
Brest,  France,  is  briefly  described.  Galleries  were  excavated 
in  the  rock  and  charged  with  black  powder,  deposited  in 
barrels  covered  by  boards  and  tar  paper  to  protect  them 
from  seepage  water.  The  galleries  were  closed  for  a  dis- 
tance of  13  ft.  by  stone  laid  in  cement  mortar,  and  then  about 
7  ft.  of  dry  stone  work  followed  by  7  ft.  of  stone  masonry 
again.  Firing  was  done  by  electricity.  The  amount  of 
powder  is  not  definitely  stated,  but  the  author  speaks  of 
40,000  Ibs.  as  being  the  maximum  blast;  and  in  the  blast 
described  104,000  cu.  yds.  were  broken,  not  a  single  stone 
being  thrown  from  the  quarry  which  was  in  a  residential 
district.  At  times  the  ratio  was  as  low  as  i  Ib.  of  powder 
to  11.7  cu.  yds.  of  rock.  The  rules  given  below  were  fol- 
lowed : 

1 i )  The  distance  between  powder  chambers  should  equal 
the  thickness  of  rock  above  them. 

(2)  The  face  left  after  a  blast  should  be  as  nearly  ver- 
tical as  possible  to  facilitate  further  work. 

(3)  With  one  powder  chamber  only,  the  distances  from 
its  center  to  the  face  of  the  quarry  and  to  the  top  of  the  mass 
should  be  equal. 

The  following  data  are  given  in  Engineering  News,  Oct. 
15,  1881: 

"A  remarkable  feat  of  railroad  building  has  recently  been 
undertaken  from  Portland  to  Dallas,  Ore.  The  road  will 
be  86  miles  long.  Much  of  the  roadway  must  be  blasted  in 
the  flinty  face  of  lofty  precipices,  or  drilled  through  no  less 
unyielding  rock.  About  10  miles  below  Dallas  is  a  bluff  of 
basaltic  rock  rising  300  ft.  from  the  Columbia  River,  along 
whose  side  the  road  is  to  pass.  Men  suspended  by  ropes  150 
ft.  over  this  wall  drill  and  blast  solid  rock,  their  work  being 
attended  with  the  greatest  danger.  The  largest  blast  on  the 
line  thus  far  has  been  at  a  point  10  miles  above  the  Cas- 


156        ROCK  EXCAVATION— METHODS  AND  COST. 

cades,  a  mass  of  rock  165  ft.  high,  170  ft.  wide  and  70  ft. 
thick  at  the  base,  containing  more  than  40,600  cu.  yds.  being 
removed  by  the  explosion  of  10,000  Ibs.  of  Judson  powder, 
equal  in  force  to  20,000  Ibs.  of  black  powder.  The  heaviest 
shot  on  this  work  was  at  'Jac°b's  Ladder.'1  At  that  point 
420  cases,  or  21,000  Ibs.,  of  Judson  powder  moved  110,000 
cu.  yds.  of  solid  rock.  At  'Shell  Rock'  56,000  cu.  yds.  of 
solid  rock  were  moved  with  10,000  Ibs.  of  Judson  powder. ' 

In  Engineering  Record  Aug.  10,  1895,  Mr.  F.  A.  Mahan 
tells  of  large  blasts  used  at  Genoa,  Italy,  in  1895.  In  lime- 
stone quarry,  strata  dipping  60°  toward  face,  galleries  were 
driven  in  the  base  at  right  angles  to  each  other,  and  then 
the  supporting  pillars  were  all  blown  out  at  once,  under- 
mining an  area  100  x  300  ft.,  allowing  the  strata  above  to 
slide  down.  When  the  strata  were  twisted  so  they  would 
not  slide,  shafts  were  sunk  from  the  top.  One  charge  of 
11,440  Ibs.  of  dynamite  produced  a  land  slide  of  260,000  cu. 
yds.  of  rock  without  damaging  surrounding  dwellings. 

A  big  blast  in  granite,  at  Long  Cove,  Me.,  is  described 
briefly  in  the  magazine,  Stone  (New  York),  1896,  p.  555, 
the  data  being  as  follows :  A  4  x  4  shaft  was  sunk  64  ft., 
then  two  drifts  were  run,  right  and  left,  each  being  27  ft. 
long;  at  the  end  of  these  drifts  cross  drifts  26  ft.  long  were 
driven,  to  receive  the  explosives.  Four  men  were  engaged 
about  &y2  mos.  doing  this  work.  Black  powder  was  charged 
in  waterproof  canvas  bags,  the  men  working  six  days  in 
complete  darkness.  In  each  of  the  two  chambers  on  the  west 
side,  1 80  kegs  were  charged ;  and  in  each  of  the  two  cham- 
bers on  the  east  side  185  kegs  were  charged,  making  all  told 
730  kegs  of  25  Ibs.  each,  or  18,250  Ibs.  Thirty-two  dyna- 
mite sticks,  each  primed  with  a  cap,  were  fired  to  explode 
the  powder.  After  the  explosion  the  ledge  was  50  ft.  higher 
than  before  (lo-ton  boulders  were  hurled  100  ft.  verti- 
cally) and  it  was  estimated  that  1,000,000  tons  of  granite 
had  been  loosened.  This  appears  to  be  altogether  too  high 
an  estimate. 


METHODS  OF  BLASTING.  157 

Blasting  Hardpan. — Hardpan,  or  cemented  gravel,  is 
usually  exceedingly  difficult  to  drill  because  of  the  "hard 
heads"  or  boulders  scattered  through  the  mass,  and  because 
of  the  clogging  of  the  drill  by  the  softer  material  encount- 
ered between  the  boulders  or  cobblestones.  If  there  are 
no  large  boulders  in  the  hardpan,  but  merely  a  mass  of 
small  pebbles  imbedded  in  clay,  or  cemented  with  iron  rust, 
a  well-drilling  machine  can  be  used  to  great  advantage.  The 
holes  drilled  by  the  well  driller  should  be  enlarged  by  spring- 
ing them  with  dynamite  and  then  charged  with  black 
powder  or  Judson  powder.  Dynamite  is  not  effective  for 
breaking  down  a  face  of  hardpan,  because  it  gives  a  sudden 
blow  that  makes  a  chamber  or  pot  hole  and  does  not  heave 
the  mass  of  hardpan  as  does  a  slower  explosive.  Joveite, 
which  strikes  a  blow  of  great  power,  but  with  less  suddenness 
than  dynamite,  has  been  used  with  economy  for  blasting 
hardpan  for  ballast  purposes  at  Cohocton,  on  the  line  of 
the  D.,  L.  &  W.  Railroad.  The  holes  were  driven  about  7 
ft.  deep,  horizontally  into  the  bank  (not  vertically),  crow- 
bars, post-hole  diggers  and  spoon  shovels  being  used  in  dig- 
ging the  holes  which  were  about  8  ins.  diam.  The  holes 
were  spaced  about  10  ft.  apart,  charged  with  4  Ibs.  of  Joveite 
in  each  hole  and  well  tamped.  This  method  of  digging  hori- 
zontal post  holes  in  the  face  of  a  gravel  bank  is  one  well 
worthy  of  remembrance. 

On  the  Chicago  Drainage  Canal  (Chapter  XIII.),  small 
tunnels  about  2  or  3  ft.  in  diameter  were  run  into  the  face 
of  the  hardpan.  If  a  large  boulder  was  encountered  the 
tunnel  was  diverted  so  as  to  pass  to  one  side  of  it.  These 
tunnels  were  driven  at  the  base  of  an  i8-ft.  face,  and  about 
1 8  ft.  center  to  center. 

The  late  Prof.  Thomas  Eggleston,  of  Columbia  Univer- 
sity, is  authority  for  the  following  data  on  bank  blasting  in 
California.  While  the  blasting  was  done  for  the  purpose 
of  breaking  up  cemented  gravel  for  hydraulicking,  it  is  evi- 


158        ROCK  EXCAVATION— METHODS  AND  COST. 

dent  that  the  same  methods  are  applicable  in  blasting  hard- 
pan  for  steam  shovel  work: 

Bankblasting  was  introduced  by  J.  F.  Pierce  in  1860, 
near  Smartsville,  Cal.  Previously  the  banks  had  been  broken 
down  by  undermining  with  picks,  not  infrequently  burying 
the  laborers.  When  very  hard  cemented  strata  make  shaft 
sinking  difficult,  then  tunnels  are  driven ;  but  when  the  bank 
is  not  very  high,  small  shafts  are  usually  sunk  and  enlarged 
in  the  form  of  a  bottle  at  the  bottom  to*  receive  the  powder. 
When  a  drift,  or  tunnel,  is  driven,  the  main  drift  has  a 
drift  at  its  end  forming  a  T.  The  end  drift  is  about  half 
as  long  as  the  main  drift.  Sometimes  a  cross  drift  is  run 
at  the  middle  of  the  main  drift,  and  has  a  length  about  one- 
third  the  length  of  the  main  drift.  The  sum  of  the  lengths 
of  all  the  cross  drifts  should  be  about  equal  to  the  length  of 
the  main  drift.  The  drifts  are  made  as  small  as  the  men 
can  work  in,  generally  3  x  4  ft.  The  length  of  the  main  drift 
is  usually  I  to  ij^  times  the  height  of  the  bank  to  be  blasted, 
if  the  bank  is  a  low  one ;  but  for  very  high  banks  its  length 
is  about  24  the  height  of  the  bank.  When  the  bank  is  80 
to  120  ft.  high  the  main  drift  is  made  about  as  long  as  the 
bank  is  high.  For  such  a  drift  about  600  (25  Ib.)  kegs  of 
powder  are  used,  400  kegs  being  placed  in  the  cross  drifts 
at  the  end  and  200  kegs  in  the  cross  drifts  at  the  middle. 
In  blasting  very  high  banks  it  has  been  found  wise  to  run 
short  main  drifts  connected  with  cross  drifts  parallel  with 
the  face  of  the  bank ;  then  to  charge  these  cross-drifts  and 
blow  out  the  gravel  between  the  cross  drifts  and  the  face  of 
the  bank,  thus  allowing  the  bank  above  to  fall  and  break  it- 
self by  its  own  weight.  In  bank  blasting  with  black  powder 
it  is  generally  calculated  that  i  Ib.  of  black  powder  will  break 
2  to  3  cu.  yds.  of  gravel.  It  is  always  better  to  use  too  much 
rather  than  too  little  powder,  for  too  little  may  result  in  the 
loss  of  the  entire  charge.  At  the  Enterprise  Mine  1,700 
(25-lb.)  kegs  were  fired  at  one  time  in  a  bank  250  ft.  high. 

In  1875  a  blast  of  17,500  Ibs.  of  powder  was  fired  at  the 


METHODS  OF  BLASTING.  159 

Paragon  claim  to  break  a  bank  150  ft.  high.  The  drifts  had 
a  total  length  of  325  ft.,  in  the  form  of  a  T.  The  main  drift 
was  no  ft.  long,  the  cross  drift  on  the  right  side  was  70  ft. 
long  and  had  at  its  end  another  55-ft.  drift  parallel  with  the 
main  drift.  The  cross  drift  on  the  left  side  was  60  ft.  long, 
and  at  its  end  had  another  drift  30  ft.  long.  The  mouth  of 
the  main  drift  was  tamped  75  ft.  from  the  end,  and  the  cross 
drifts  were  tamped  10  ft.  each  way  from  the  main  drift, 
which,  with  the  width  of  the  drift,  made  100  ft.  of  tamping. 
A  large  amount  of  open  space  was  left  in  the  L  drifts  for 
the  expansion  of  the  gases.  The  electric  battery  was  450  ft. 
from  the  mouth  of  the  tunnel,  and  the  total  length  of  wire 
was  1,500  ft.  The  running  of  the  drift  cost  $300,  and  the 
explosives  cost  $2,700. 

A  blast  of  50,000  Ibs.  of  black  powder  was  fired  at  the 
Blue  Point  Gravel  Mine  in  1870  that  lifted  150,000  cu.  yds. 
(i  Ib.  to  3  cu.  yds.)  of  gravel  vertically  a  distance  of  6  to 
10  ft.  The  main  drift  (3  x  4  ft.)  was  275  ft.  long.  On  the 
left  there  were  six  side  drifts,  each  120  ft.  long,  the  first  one 
being  75  ft.  from  the  mouth  of  the  main  drift.  On  the  right 
there  were  six  side  drifts,  each  80  ft.  long.  On  the  first  drift 
to  the  right  was  a  drift  15  ft.  long  parallel  with  the  main 
drift.  The  powder  was  equally  distributed  through  the 
drifts,  and  was  fired  by  electricity  from  ten  different  points. 

In  1875,  at  the  Dardenelles  Mine,  36,000  Ibs.  of  Judson 
powder  broke  up  500,000  cu.  yds.  of  cement  gravel — a  ratio 
of  i  Ib.  to  14  cu.  yds. — although  Judson  powder  is  commonly 
regarded  by  bank  blasters  as  being  twice  as  effective  as 
black  powder  pound  for  pound.  The  face  of  the  bank  was 
175  ft.  high  and  1,000  ft.  long.  Into  this  face  five  parallel 
drifts  were  run,  across  each  of  which  two  or  more  cross 
drifts  were  cut  at  right  angles.  The  total  length  of  drifts 
was  1,200  ft.  The  powder  was  charged  in  28  lots  of  1,000 
to  2,500  Ibs.,  in  each  of  which  were  placed  three  electric  ex- 
ploders. 


160        ROCK  EXCAVATION— METHODS  AND  COST. 

In  1881  at  the  Blue  Tent  Mine  43,000  Ibs.  of  black  powder 
were  fired  under  a  bank  200  ft.  high. 

In  1872,  at  the  Harriman  and  Taylor  claim,  3,500  Ibs.  of 
dynamite  broke  down  200,000  cu.  yds.  of  gravel,  a  ratio  of 
I  Ib.  to  57  cu.  yds.  This  seems  to  be  a  very  high  ratio,  for 
Prof.  Eggleston  tells  of  2,500  Ibs.  of  dynamite  loosening 
75,000  to  100,000  cu.  yds.,  or  I  Ib.  to  30  or  40  cu.  yds.,  and 
adds  that  i  Ib.  of  dynamite  is  as  effective  as  5  or  6  Ibs.  of 
black  powder,  which,  however,  does  not  accord  with  the 
data  of  the  blasts  cited  by  him.  While  dynamite  in  small 
charges  in  drill  holes  is  not  effective  for  bank  blasting,  as 
I  have  had  occasion  to  ascertain  by  test  more  than  once,  it 
appears  to  have  been  very  effective  when  fired  in  drifts 
which  were  undoubtedly  not  packed  solid  with  tamping,  but 
in  which  large  air  spaces  were  left. 

Blasting  Piles  and  Stumps. — In  Engineering  News  April 
16,  1903,  I  have  given  data  on  pile  blasting  based  upon 
methods  that  I  used  in  removing  several  hundred  white  oak 
piles  from  the  bed  of  the  Chemung  River,  New  York.  The 
piles  had  been  sawed  off  at  low  water  level,  when  the  river 
was  "waist  deep."  With  a  ship  auger  a  hole  was  bored 
down  the  heart  of  the  pile  a  distance  of  4  or  5  ft.,  and  then 
3  or  4  sticks  (l/2  Ib.  each)  of  40  per  cent,  dynamite  were 
placed  in  the  hole,  tamped  with  water  and  fired.  The  result 
was  merely  to  splinter  the  oak  into  whipcords.  After  some 
further  experimenting  I  found  that  two  l/2  Ib.  sticks  of  70 
per  cent,  dynamite  and  one  stick  of  40  per  cent,  dynamite  in 
each  hole  would  cut  the  largest  pile  off  below  the  bed  of  the 
river  and  hurl  the  top  50  to  100  ft.  up  into  the  air.  Ship 
augers  boring  a  hole  \y2  in.  in  diameter  and  4^  ft.  deep 
were  used.  One  laborer  bored  7  such  holes  per  ic-hr.  day, 
at  a  cost  of  21  cts.  per  pile  for  boring;  i  Ib.  of  70  per  cent, 
dynamite  at  20  cts.  a  Ib.,  and  l/2  Ib.  of  40  per  cent,  at  15  cts. 
a  Ib.,  made  the  cost  of  powder  28  cts.  per  pile.  To  this  was 
added  5  ft.  of  fuse  costing  3  cts.,  and  a  cap,  I  ct.,  making  a 
total  cost  of  55  cts.  per  pile  for  boring  and  explosives.  Two 


METHODS  OF  BLASTING.  161 

men  would  load  and  fire  100  holes  a  day,  using  water  tamp- 
ing. Once  in  a  while  a  very  tough  pile  would  resist  the 
dynamite,  leaving  a  splintered  snag. 

Mr.  G.  W.  Stadly,  in  a  letter  commenting  upon  the 
method  of  pile  blasting,  gives  the  following:  It  was  neces- 
sary to  remove  the  piles  used  for  falsework  in  a  river.  Rings 
that  would  just  slip  over  a  pile  were  made  of  telegraph  wire. 
On  each  ring  were  fastened  three  half-sticks  of  40  per  cent, 
dynamite  in  separate  places,  and  an  electric  cap  placed  in 
each  stick.  The  rings  were  dropped  over  the  piles  to  the 
bottom  of  the  river,  after  attaching  the  electric  wires,  and, 
upon  firing,  each  pile  was  cut  off  clean,  without  splintering. 
It  is  probable  that  the  piles  were  of  some  soft  wood  like  pine 
or  spruce.  Eissler  states  that  a  tree  stump  30  ins.  diam. 
was  sawed  off  at  the  surface  of  a  river,  and  three  vertical 
holes  (iy2  in.)  were  bored  with  augers  to  depths  of  4^,  8 
and  8^  ft.,  requiring  3  hrs.  for  the  short  hole  and  4^2  hrs. 
for  each  of  the  others.  A  charge  of  I  Ib.  of  dynamite  was 
fired  in  each  hole. 

Stumps  may  be  blasted  out  either  with  dynamite  or  with 
black  powder.  A  hole  is  bored  in  the  earth  until  the  end  of 
the  hole  is  directly  under  the  center  of  the  stump.  If  the 
soil  is  clay,  an  earth  auger  may  be  used,  or  an  iron  bar  may 
be  churned  or  driven  down  with  hammers.  If  the  soil  is 
dry  sand,  the  hole  will  fill  up  as  soon  as  the  drill  is  with- 
drawn unless  some  precaution  is  taken.  I  have  found  a 
neat  way  to  hold  the  sand  is  to  saturate  it  with  water  around 
the  bore  hole.  This  may  be  done  by  using  a  gas  pipe  for 
the  drill.  Drive  the  pipe  down  a  little  way  and  pour  water 
in  at  the  top,  and  repeat.  If  holes  are  drilled  in  the  sides 
of  the  pipe  near  its  lower  end  the  water  will  run  out  and 
saturate  the  sand,  so  that  when  the  pipe  is  withdrawn  the 
hole  will  remain  open.  For  small  stumps  half  a  stick  to  a 
stick  of  40  per  cent,  dynamite,  well  tamped,  will  serve.  In 
blasting  stumps  2  to  8  ft.  in  diameter,  the  hole  may  be  sprung 
(unless  in  dry  sand)  by  firing  a  small  charge  of  dynamite, 


i62        ROCK  EXCAVATION— METHODS  AND  COST. 

and  the  chamber  so  formed  loaded  with  black  powder  In 
this  way  a  keg  (25  Ibs.)  of  black  powder  will  throw  out 
the  stump  of  a  6  ft.  fir  tree.  Judson  powder  is  very  effective 
for  large  stumps.  In  heavy  soils  place  the  hole  so  that 
the  charge  of  explosive  will  be  close  to  the  roots;  but  in 
light  soils  the  powder  should  be  buried  deeper.  Where  the 
roots  spread  so  as  to  cover  a  large  area  the  charge  must  be 
placed  deeper.  In  some  stumps,  such  as  second  growth 
chestnut,  the  rotten  stump  of  the  first  growth  lies  directly 
beneath  the  new  tree ;  in  which  case  the  dynamite  will  mere- 
ly scatter  the  old  punk  and  not  blow  out  the  new  stump.  If 
a  large  flat  stone  is  shoved  under  the  new  stump,  between 
the  roots,  a  stick  of  dynamite  laid  upon  it  and  earth  packed 
over  it,  the  explosion  will  be  effective. 

Ice  Blasting. — To  open  a  channel  through  solid  ice,  bore 
holes  through  the  ice  with  augers,  and  suspend  dynamite 
charges  of  ^2  lb.  to  5  Ibs.  each  from  ^2  ft.  to  5  ft.  under  the 
ice.  Solid  fresh  water  ice,  3  ft.  thick,  has  been  broken  in 
a  circle  60  to  70  ft.  in  diameter  by  4  Ibs.  of  dynamite.  Rot- 
ten, salt  water  ice,  10  ins.  thick,  has  been  broken  in  a  circle 
20  ft.  diam.  by  y2  lb.  of  dynamite  exploded  i^  ft.  under 
the  ice.  Experiments  should  be  made  increasing  the  size 
and  depth  of  the  charge  until  the  maximum  area  is  broken 
per  pound  of  dynamite.  Charges  of  1-3  lb.  of  dynamite 
have  been  fired  within  2  ft.  of  piling,  clearing  the  ice  from 
the  piles  without  damaging  them.  Ice  jams  above  bridges 
can  often  be  broken  up  by  firing  charges  of  5  to  25  Ibs.  of 
dynamite.  The  foregoing  data  on  ice  blasting  are  given  in 
a  catalogue  on  Atlas  Powder  by  the  Repauno  Chemical  Co. 

Boulder  Blasting. — There  are  three  ways  of  breaking  up 
a  boulder  with  explosives:  (i)  Block-holing;  (2)  mud- 
capping;  and  (3)  undermining.  Block-holing  consists  in 
drilling  a  shallow  hole  in  the  boulder  and  exploding  a  small 
charge  of  high  power  explosive  in  the  hole.  Mud-capping 
consists  simply  in  firing  some  dynamite  on  top  of  the  boul- 
der, after  covering  it  with  a  shovelful  of  earth,  preferably 


METHODS  OF  BLASTING.  163 

wet  clay.  Undermining  consists  in  boring  a  hole  in  the 
earth  and  firing  a  charge  of  dynamite  or  Joveite  in  the  hole 
directly  beneath  the  boulder.  Block-holing  is  obviously  the 
most  effective  way  of  using  the  explosive,  and  it  is  surpris- 
ing how  small  a  charge  of  75  per  cent,  dynamite  in  a  block 
hole  will  break  a  huge  granite  boulder.  The  cost  of  drilling 
is  greatly  reduced  wherever  pneumatic  plug  drills  (see  page 
189)  are  used.  In  the  Homestake  Mine  plug  drills  have 
largely  displaced  hand  drills  for  the  purpose  of  block-holing 
chunks  of  rock  too  large  to  sledge  economically. 

Mud-capping  is  very  wasteful  of  powder,  and  should  only 
be  used  where  a  few  scattering  boulders  are  to  be  broken. 
The  "mud"  tamping  is  obviously  not  sufficient  to  enable  the 
explosive  to  do  its  best  work.  Undermining  is  more  effec- 
tive than  mud-capping,  because  the  boulder  then  acts  as  its 
own  tamping;  but  very  often  the  earth  beneath  the  boulder 
is  such  that  boring  in  it  is  too  expensive,  or  it  may  happen 
that  the  boulder  rests  upon  rocks.  For  data  on  the  cost  of 
blasting  boulders,  see  page  232. 


CHAPTER  X. 
COST   OF   LOADING   AND   TRANSPORTING. 

Cost  of  Loading  by  Hand. — Where  a  laborer  has  merely 
to  pick  up  and  cast  one-man  stone  into  a  jaw  crusher,  I  have 
had  men  average  34  cu.  yds.  of  loose  stone  handled  per  man 
per  lo-hr.  shift,  which  is  equivalent  to  about  20  cu.  yds.  of 
solid  rock.  This,  I  believe,  marks  the  maximum  that  may 
be  done,  day  in  and  day  out,  by  a  good  worker,  where  the 
stone  has  scarcely  to  be  lifted  off  the  floor  to  toss  it  into  the 
jaws.  Every  stone,  however,  was  handled  and  not  shoved 
or  slid  into  the  crusher.  Going  to  the  other  extreme,  where 
conditions  are  not  favorable,  where  there  are  more  or  less 
delays  at  blasting,  where  there  is  some  sledging  and  a  little 
track  laying,  and  where  delays  in  getting  cars  are  frequent, 
as  in  railway  tunneling,  one  man  will  load  about  3  cu.  yds. 
of  solid  rock  per  shift  (the  range  being  from  2  to  5  cu.  yds., 
as  given  in  Chapter  XVI. ). 

On  the  Chicago  Canal  (see  page  262)  the  average  out- 
put per  man  per  lo-hr.  shift  was  about  7  cu.  yds.  loaded  into 
dump  cars,  and  this  included  some  sledging.  The  average 
per  man  loading  into  the  low  skips  used  on  the  cableways, 
involving  very  little  sledging,  was  about  10  cu.  yds.  of  solid 
rock  per  man  per  lo-hr.  shift.  The  best  day's  record  was 
16.6  cu.  yds.  per  man  loading  into  skips.  In  loading  cars 
about  5  men  out  of  the  force  of  36  loaders  were  kept  busy 
sledging  the  rock;  but  with  the  cableways  not  only  was  it 
easier  to  roll  large  rocks  into  the  skips  (or  "scale  pans"), 
but  very  large  rocks  were  lifted  with  grab  hooks  and  chains 
and  carried  to  the  dump  without  sledging. 

In  loading  wagons  with  stone  easily  lifted  by  one  man, 
the  wagon  having  high  sides,  I  have  found  that  a  man  will 
readily  average  10  cu.  yds.  solid,  which  is  equivalent  to  17 

164 


COST   OF  LOADING   AND    TRANSPORTING.        165 

cu.  yds.  loose  measure  per  day  of  10  hrs.  The  same  man 
will  throw  the  stone  out  of  the  wagon  twice  as  fast  as  he 
will  load  it,  and  this  does  not  mean  dumping  the  wagon, 
but  handling  each  stone  separately.  In  loading  a  wagon 
having  a  stone-rack,  and  no  sides,  two  men,  passing  stone 
up  to  the  driver  who  cords  the  stone  on  the  rack,  will  load 
i  cu.  yd.  solid  stone  in  13  mins.  when  working  rapidly,  but 
this  is  too  high  an  average  to  be  maintained  steadily  for  a 
full  day.  A  driver  will  unload  I  cu.  yd.  solid  (or  1.7  cu.  yd. 
loose)  from  such  a  stone-rack,  by  rolling  the  stone  off,  in  7 
mins.  if  he  hurries,  but  he  may  take  20  mins.  if  he  loafs.  A 
man  will  readily  load  a  wheelbarrow  with  stone  already 
sledged  and  ready  for  the  crusher  at  the  rate  of  12  cu.  yds. 
solid  (or  21  cu.  yds.  loose)  in  10  hrs. 

Croes  is  authority  for  the  statement  that  on  Boyd's  Cor- 
ner Dam  rough  rubble  stone  was  loaded  onto  wagons  at 
the  rate  of  13  cu.  yds.  per  man  in  10  hrs.,  which  is  equiva- 
lent to  1 1^2  cts.  per  cu.  yd.,  wages  being  15  cts.  per  hr.  The 
cut  stone  for  this  dam,  during  the  years  1868-1869,  cost 
about  30  cts.  per  cu.  yd.  to  load  on  stone  trucks,  but  in  the 
year  1870  the  cost  was  reduced  to  13  cts.  per  cu.  yd.,  wages 
being  15  cts.  per  hr.,  although  it  is  not  stated  how  this  re- 
duction was  effected. 

In  quarrying  mica  schist  for  rough  rubble  in  upper  New 
York  City,  according  to  Mr.  John  J.  Hopper  the  cost  of 
loading  wagons  was  25  cts.  per  cu.  yd.,  the  rate  of  wages 
being  15  cts.  per  hr. 

In  moving  several  hundred  yards  of  stone  for  rip-rap  I 
have  had  5  laborers  load,  haul  500  ft.  on  a  flat  hand  car  and 
unload,  at  the  rate  of  10  cu.  yds.  solid  measure  (17  cu.  yds. 
loose)  in  9  hrs.  per  man.  The  stone  was  one  and  two-man 
stone,  and  was  handled  twice,  once  in  loading  and  once  in 
unloading. 

Cost  of  Handling  Crushed  Stone. — In  handling  stone  after 
it  has  been  crushed  to  2 y2 -in.  size,  or  smaller,  a  shovel  is 
used,  and  the  output  of  a  man  depends  very  largely  upon 


166        ROCK  EXCAVATION— METHODS  AND  COST. 

whether  he  is  shoveling  stone  that  lies  upon  smooth  boards 
or  whether  it  lies  upon  the  ground.  I  have  often  had  6  good 
shovelers  unload  a  canal  boat  holding  120  cu.  yds.  loose 
measure  of  crushed  trap  rock  (2-in.  size)  in  9  hrs.,  but  after 
breaking  through  to  the  floor  the  shoveling  was  compara- 
tively easy;  this  is  20  cu.  yds.  loose  (or  12  cu.  yds.  solid) 
per  man  per  day  shoveled  into  skips.  In  shoveling  from 
flat  cars  into  wagons  the  same  rate  can  be  attained,  but  in 
shoveling  from  a  hopper-bottom  car,  where  there  is  at  no 
time  a  smooth  floor  along  which  to  force  the  shovel,  an 
output  of  14  cu.  yds.  loose  measure  (or  8  cu.  yds.  solid)  is 
a  fair  lo-hr.  day's  work.  In  shoveling  broken  stone  off  the 
ground  into  wagons  it  is  not  safe  to  count  upon  much  more 
than  12  cu.  yds.  loose  measure  (or  7  cu.  yds.  solid)  per 
man  per  10  hrs.  A  careful  manager  will,  if  possible,  pro- 
vide a  smooth  platform,  preferably  faced  with  sheet  iron, 
upon  which  to  dump  any  stone  that  is  to  be  re-handled  by 
shovelers.  Small  stone,  y^  in.  or  less  in  diameter,  is  easily 
penetrated  by  a  shovel  and  need  not  be  dumped  upon  a  plat- 
form. A  chamshell  bucket  operated  by  a  locomotive  crane 
is  doubtless  the  most  economic  method  of  loading  broken 
stone  from  cars  or  stock  piles,  where  the  quantity  to  be 
handled  warrants  the  installation. 

Cost  of  Handling  with  a  Derrick. — Where  crushed  stone 
must  be  handled  with  a  derrick,  as  in  unloading  boats,  I 
have  found  the  following-  to  be  about  the  best  that  can  be 
done  per  day :  Per  day. 

6  shovelers,  at  $1.50 $9.00 

1  hooker  on    1.50 

2  tagmen 3.00 

I   dumpman    1.50 

i  water  boy i.oo 

I  team  on  derrick 3.50 

I  foreman  3.00 


120  cu.  yds.  (loose)  at  19  cts.  = $22.50 


COST   OF   LOADING   AND    TRANSPORTING.         167 

It  commonly  costs  about  25  cts.  per  cu.  yd.  (loose  meas- 
ure) to  unload  a  boat  of  broken  stone  using  skips  holding 
1 8  cu.  ft.  each,  and  a  team  on  the  derrick  for  raising  them. 
Where  any  great  amount  of  such  work  is  to  be  done,  how- 
ever, a  hoisting  engine  and  a  derrick  provided  with  a  bull- 
wheel  should  be  used.  The  following,  from  my  note  book, 
shows  the  cost  of  unloading  flat  cars  containing  broken 
stone  (2-in.  size),  using  a  derrick  with  a  bull- wheel  for 
"slewing"  the  boom : 

5  shovelers,  at  $1.50 $7-5o 

i  dumpman    1.50 

i  engineman 2.50 

y2  ton  coal  at  $3 1.50 

100  cu.  yds.  (loose)  at  13  cts.  = $13.00 

In  this  case  a  stiff-leg  derrick,  4O-ft.  boom,  with  a  bull- 
wheel,  operated  by  a  double  cylinder  (?x  10)  engine,  han- 
dled self-righting  steel  buckets  holding  20  cu.  ft.  each.  Water 
for  the  engine  was  delivered  in  a  pipe.  The  engineman 
was  the  foreman. 

In  neither  of  the  two  cases  just  cited  is  the  cost  of  install- 
ing the  derrick  included,  nor  is  the  interest  and  depreciation 
of  plant  included.  It  takes  6  men  and  a  foreman  one  day 
to  dismantle  and  move  a  stiff-leg  derrick  a  short  distance 
(100  or  200  ft.),  and  one  more  day  to  set  it  up  again.  This 
includes  moving  the  engine  and  the  stones  used  to  hold  the 
stiff  legs  down ;  and  it  applies  to  a  slow  gang  of  workmen. 

A  guy  derrick  with  a  50  or  6o-ft.  boom  swung  by  a  bull- 
wheel  and  a  hoisting  engine  will  often  prove  the  cheapest 
device  for  loading  cars  with  blasted  rock.  If  the  derrick 
is  handling  skips  loaded  with  stone,  the  following  is  a  fair 
average  of  the  time  elements  in  handling  each  skip  load: 

Changing  from  empty  to  loaded  skip 35  sees. 

Swinging  (half  circle)   20 


168        ROCK  EXCAVATION— METHODS  AND  COST. 

Dumping  skip   15  sees. 

Swing  back    20     " 

Total    90     " 

If  there  were  no  delays,  it  would  be  possible  to  handle  400 
skip  loads  in  10  hrs.  Usually,  however,  the  loaders  will 
cause  more  or  less  delay,  so  that  it  is  safer  to  count  upon 
what  they  will  average  rather  than  upon  what  the  derrick 
can  do.  One  derrick  cannot  serve  a  very  long  face,  and  the 
number  of  men  that  can  be  worked  to  advantage  in  a  given 
space  is  always  limited;  hence  I  repeat  that  with  a  good 
derrick  provided  with  a  bull-wheel  the  derrick  can  ordi- 
narily handle  more  stone  than  can  be  delivered  to  it  by  the 
men.  The  economic  size  of  the  skip  load  is  entirely  de- 
pendent upon  the  size  of  the  hoisting  engine,  but  a  com- 
mon size  skip  measures  5  x  6  ft.  x  14  ins.  deep.  Where 
much  work  is  to  be  done  a  contractor  should  never  try  to 
get  along  with  a  derrick  not  provided  with  a  bull-wheel  for 
"slewing"  the  boom,  for  the  wages  of  two  tagmen  would 
soon  pay  for  a  new  outfit. 

Cost  of  Loading  with  Steam  Shovels. — A  contractor  who 
has  never  had  experience  in  handling  hard  rock  with  steam 
shovels  is  almost  certain  to  overestimate  the  probable  out- 
put of  a  shovel  loading  rock.  This  is  due  very  largely  to 
the  common  tendency  to  think  of  all  rock  as  being  a  ma- 
terial that  differs  only  to  a  moderate  degree  in  hardness. 
Then  again  perhaps  the  frequently  published  accounts  of 
steam  shovels  used  to  load  iron  ore  have  had  a  tendency  to 
mislead  the  inexperienced  man.  The  iron  ore  of  the  Messaba 
Range,  for  example,  is  in  reality  a  material  that  often  re- 
quires no  blasting  and  may  be  dug  out  of  the  bank  with  a 
powerful  steam  shovel  using  a  small  dipper.  It  should  not 
be  classed  as  a  rock,  but  rather  as  a  weak  shale,  so  far  as  co- 
hesive strength  is  concerned. 

A  soft  shale  that  can  be  dug  without  blasting  is  just  as 
much  a  rock  as  the  toughest  granite.  Yet  when  it  comes 


COST  OF  LOADING  AND    TRANSPORTING.         169 

to  loading  rock  with  a  steam  shovel  there  is  all  the  difference 
imaginable  between  shales  and  granites.  Practically  all 
printed  records  of  shovels  working  in  rock  refer  to  shale, 
hardpan  and  soft  iron  ore.  The  only  printed  records  of 
shovel  output  in  tough  rock  that  blasts  out  in  large  chunks 
are,  so  far  as  I  know,  the  records  kept  by  the  engineers  on 
one  section  of  the  Chicago  Drainage  Canal.  I  have  given 
these  records  in  full  on  page  265.  Two  55-ton  shovels,  each 
working  two  lo-hr.  shifts  a  day  for  four  months,  averaged 
296  cu.  yds.  of  solid  rock  (limestone)  per  shovel  per  shift 
loaded  into  cars,  although  it  is  stated  that  one  day  one  of  the 
shovels  loaded  600  cu.  yds.  of  rock  in  10  hrs.  The  lime- 
stone on  the  Chicago  Canal  did  not  break  up  into  small 
pieces  upon  blasting  (a  condition  that  is  essential  to  eco- 
nomic steam  shovel  work  in  rock),  but  it  came  out  in  large 
chunks,  much  of  which  had  to  be  lifted  with  chains,  instead 
of  being  scooped  up  by  the  dipper.  When  each  separate 
rock  must  be  "chained  out"  in  this  way,  a  steam  shovel  is 
really  no  better  than  a  derrick,  and  is,  in  fact,  not  so  good. 
On  a  large  contract  near  New  York  City,  where  the  rock 
is  a  tough  mica  schist  that  breaks  out  in  large  chunks  even 
with  close  spacing  of  holes,  a  65-ton  shovel  with  a  2^4-cu. 
yd.  dipper  averaged  for  several  weeks  about  280  cu.  yds.  of 
solid  rock  loaded  on  to  cars.  Part  of  this  rock  was  loaded 
with  the  dipper  and  part  was  chained.  Four  men  in  the  pit 
would  fasten  a  chain  around  a  large  rock  and  throw  the 
hook  of  the  chain  over  one  of  the  dipper  teeth.  The  shovel 
would  then  deliver  the  rock  to  the  car  where  a  man  un- 
hooked the  chain.  The  time  required  for  these  four  pit 
men  to  fasten  the  chain  around  a  rock  ranged  from  1-3  min. 
to  2^4  mins.,  and  on  the  average  was  about  I  min.  The 
operation  of  swinging  the  dipper  both  ways  and  unhooking 
the  rock  averaged  about  50  sees.  Thus  a  rock  every  2  mins. 
was  averaged  when  working  steadily;  but  delays  due  to 
shipping  of  chains,  etc.,  would  bring  the  average  down  to 
about  one  rock  every  2^2  mins.,  or  about  240  rocks  in  10 


i;o        ROCK  EXCAVATION— METHODS  AND  COST. 

hrs.  Each  rock  did  not  average  much  to  exceed  ^4  cu-  yd., 
since  the  rock  broke  out  in  long  flat  slabs — too  long  to  enter 
the  dipper,  although  much  smaller  in  cubic  contents  than 
the  dipper  capacity.  One  of  the  features  that  should  not  be 
lost  sight  of  in  such  work  is  the  necessity  of  close  spacing 
of  drill  holes  in  order  to  break  up  the  rock  to  sizes  such  that 
at  least  a  part  of  the  chunks  will  enter  the  dipper.  In  this 
case  the  holes  were  spaced  about  4^2  ft.  apart.  The  fore- 
man of  this  shovel  work  certainly  did  not  handle  rock  with 
the  chain  as  fast  as  could  have  been  done,  for  he  should 
have  provided  an  extra  chain  which  the  men  could  have  been 
fastening  to  another  rock  while  the  shovel  was  unloading 
into  the  car. 

On  the  Jerome  Park  Reservoir  excavation  in  New  York 
City  the  rock  is  also  a  tough  mica  schist  that  blasts  out  in 
slabs  even  with  heavy  blasting.  I  am  informed  by  Mr.  R.  C. 
Hunt,  manager  for  Mr.  John  B.  McDonald,  contractor,  that 
their  7o-ton  shovels  loaded  only  300  cu.  yds.  of  solid  rock 
per  lo-hr.  shift.  Mr.  Hunt  says: 

This  was  in  the  gneiss  rock  (mica-schist)  of  this  vicinity.  The 
fibrous  nature  of  Manhattan  and  adjacent  rocks  causes  it  to  break 
in  such  large  and  awkwark  shapes  that  the  shovel  cannot  do  itself 
justice.  I  therefore  abandoned  the  use  of  shovels  in  the  rock  cuts 
and  find  that  I  can  handle  the  rock  with  derricks  more  economically. 

This  statement  agrees  very  closely  with  my  own  observa- 
tion of  other  contract  work  on  Manhattan,  as  above  re- 
corded. At  the  times  of  my  visits  to  the  Jerome  Park  work 
the  holes  were  being  drilled  as  follows :  The  face  was  35 
ft.  high,  and  three  rows  of  vertical  holes  were  put  down  25 
ft.,  the  rows  of  holes  being  5  ft.  apart  and  the  holes  in  each 
row  7^2  ft.  apart.  A  row  of  nearly  horizontal  holes  was 
drilled  35  ft.  below  the  top  of  the  face,  the  holes  being  5  ft. 
apart.  All  holes  were  loaded  with  dynamite  and  fired  to- 
gether. The  five  shovels  were  loading  on  to  standard  gauge 
flat  cars  which  were  unloaded  at  the  dump  with  a  Lidger- 
wood  plow  and  hoisting  engine ;  the  cuts  were  side  cuts. 

In  thorough  cut  work  on  the  Wabash  Railroad,  one  42- 


COST   OF  LOADING  AND    TRANSPORTING.         171 

ton  shovel  loaded  240  cu.  yds.  of  sandstone  (solid  measure) 
into  dump  cars  in  10  hrs.,  as  an  average  of  a  year's  work ; 
but  about  10  per  cent,  of  the  working  time  was  lost  in  break- 
downs, etc. 

In  shale,  or  any  friable  rock  that  breaks  up  into  pieces 
that  readily  enter  the  dipper,  the  output  of  a  steam  shovel 
is  far  greater  than  in  hard  rock  such  as  I  have  been  citing. 
Through  the  kindness  of  Mr.  George  Nauman,  assistant  en- 
gineer, Pennsylvania  Railroad,  I  am  able  to  give  the  out- 
put of  several  shovels  working  more  than  a  year,  in  shale 
near  Enola,  Pa.  Each  shovel  worked  two  lo-hr.  shifts  per 
day,  six  days  in  the  week.  In  cut  No.  I  there  were  nearly 
2,000,000  cu.  yds.,  of  which  85  per  cent,  was  rock.  Of  this 
rock  a  little  was  very  hard  limestone,  some  was  blue  shale 
nearly  as  hard,  and  most  of  it  was  red  shale,  somewhat  soft- 
er. Excluding  the  first  two  months,  the  average  output  of 
each  shovel  per  month  of  double-shift  work  was  nearly 
31,000  cu.  yds.,  equivalent  to  15,500  cu.  yds.  single-shift 
work.  There  were,  on  an  average,  four  shovels  at  work, 
averaging  60  tons  weight  per  shovel.  The  best  month's 
output  was  47,300  cu.  yds.  per  shovel  in  August,  1903,  and 
the  poorest  month  (after  work  was  well  started)  was 
20,800  cu.  yds.  per  shovel  in  February,  1904,  working  double 
shifts.  In  cut  No.  2  there  were  1,130,000  cu.  yds.  of  red 
shale,  and  while  the  monthly  output  per  shovel  was  some- 
what less  than  in  cut  No.  I,  the  digging  was  somewhat  bet- 
ter. Three  shovels  were  engaged  13  months,  and  each  aver- 
aged 29,500  cu.  yds.  per  month  of  double-shift  work,  equiva- 
lent to  14,750  cu.  yds.  of  single-shift  work.  The  average 
weight  of  each  shovel  was  60  tons.  The  best  month's  work 
was  December,  1903,  in  which  each  shovel  averaged  41,480 
cu.  yds.  working  double-shifts ;  the  poorest  month  was  Jan- 
uary, 1904,  in  which  each  shovel  averaged  23,850  cu.  yds. 
The  Allison  dump  cars  used  in  this  work  have  a  capacity  of 
about  4  cu.  yds.  struck  measure ;  but,  although  heaped,  the 
average  car  holds  only  2.5  cu.  yds.  of  shale  measured  in 


172        ROCK  EXCAVATION— METHODS  AND  COST. 

place.  The  cuts  were  all  side  cuts.  I  spent  considerable  time 
in  studying  the  excavation  work  being  done  during  1903 
between  Pittsburg  and  Philadelphia.  Just  west  of  Harris- 
burg  there  were  13  steam  shovels  at  work  removing  some 
4,000,000  cu.  yds.  (mostly  shale)  for  the  new  gravity  yards 
of  the  Pennsylvania  Railroad.  For  the  most  part  the  cuts 
were  side-hill  cuts,  and  the  grades  of  the  temporary  tracks 
were  so  level  that  a  "dinkey"  readily  hauled  a  train  of  10 
cars,  each  holding  2.5  cu.  yds.  of  shale,  place  measure.  Each 
shovel  was  served  by  from  two  to  six  trains  of  cars,  de- 
pending upon  the  length  of  haul,  and  there  were  few  delays 
in  waiting  for  cars — a  vital  point  in  securing  economic  re- 
sults. I  found  that  the  night  shifts  loaded  about  20  per  cent, 
less  material  than  the  day  shifts.  The  crew  serving  each 
shovel  consisted  of  6  pitmen,  I  pit  boss,  I  dipperman,  I 
craveman,  I  fireman,  3  locomotive  engineers,  3  trainmen, 
i  switchman,  12  dumpmen  and  i  dump  boss.  There  were, 
besides,  about  12  trackmen  to  each  shovel  grading  new 
tracks,  building  temporary  trestles,  shifting  track,  etc.  Most 
of  the  drilling  of  blast  holes,  which  I  have  described  in 
Chapter  V.,  was  done  with  well  drillers.  The  shale  broke 
up  well  upon  blasting,  often  looking  like  a  mass  of  chips. 
About  550  cu.  yds.  of  shale  loaded  per  lo-hr.  shift  was 
averaged  by  each  6o-ton  shovel,  including  all  delays,  work- 
ing in  side  hill  cuts  averaging  about  24  ft.  deep. 

I  am  indebted  to  Mr.  T.  S.  Bullock,  President  and  General 
Manager,  Sierra  Railway  Co.,  of  California,  for  the  follow- 
ing data:  This  company  has  two  43-ton  Marion  steam 
shovels  with  iJ/2-yd.  dippers.  One  of  these  shovels  worked 
from  April  i,  1903,  to  April  i,  1904,  in  slate  rock,  all  of 
which  had  to  be  blasted.  In  300  working  days  of  10  hrs. 
each  this  shovel  loaded  199,000  cu.  yds.  into  small  horse 
cars,  which  is  equivalent  to  663  cu.  yds.  per  shift.  Had 
large  cars  been  used  the  output  would  probably  have  been 
15  to  20  per  cent,  greater.  There  were  days  when  800  to 
900  cu.  yds.  were  loaded,  and  at  other  times  there  were  de- 


COST   OF  LOADING   AND    TRANSPORTING.         173 

lays  in  waiting  for  cars,  when  only  400  or  500  cu.  yds.  were 
loaded.    This  is  an  excellent  record  for  a  year's  work. 

I  am  indebted  to  Mr.  Daniel  J.  Hauer  for  the  following 
information:  With  a  65-ton  shovel,  provided  with  a  rock 
dipper  (shallow  and  broad)  having  a  capacity  of  2^  cu. 
yds.,  the  output  for  four  months  was  15,000  cu.  yds.  per 
month,  working  two  lo-hr.  shifts  per  day.  The  drill  holes 
were  35  to  50  ft.  deep,  and  the  rock  was  granite  and  gneiss, 
somewhat  disintegrated  in  places.  The  drilling  was  done 
by  hand  with  churn  drills,  taking  6  men  to  pull  a  drill.  The 
crews  were  as  follows: 

6  men,  pit  crew 
8  men,  drill  crew 
i  drill  foreman 
1 8  men,  dump  crew 
'    i  dump  foreman 
6  men,  extra  crew 
i  foreman. 

The  "extra  crew"  at  times  worked  on  the  dump  or  helped 
the  drilling  crew,  and  two  men  were  used  to  run  a  steam 
drill  (receiving  steam  from  the  shovel  boiler)  in  drilling 
block  holes.  The  cost  of  repairs  to  the  shovel  was  very  high. 
The  total  cost  for  wages  (double  shift  work),  supplies,  ex- 
plosives, etc.,  was  about  $8,500  per  month.  The  large  num- 
ber of  men  on  the  dump  was  due  to  the  fact  that  the  rock 
was  all  rehandled  in  widening  a  fill. 

Cost  of  Steam  Shovel  Work  in  Iron  Ore. — I  am  indebted  to 
Mr.  Daniel  King,  General  Manager  Pinkney  Mining  Co., 
Pinkney,  Tenn.,  for  the  following  data :  Two  43-ton  shovels 
(i/^-yd.  dippers),  are  worked  in  side  cuts  25  ft.  high.  The 
ground  is  generally  shaken  up  in  front  of  the  shovel,  a  20- ft. 
hole,  12  to  16  ft.  back  of  the  face,  being  sprung  with  2  to  5 
sticks  of  dynamite  and  then  shot  with  2  to  4  kegs  of  powder. 
The  ore,  which  varies  from  the  consistency  of  hard  pan  to 
ordinary  earth,  is  merely  shaken  up  and  not  thrown  down. 
The  dump  cars  hold  77  cu.  ft.  level  full  and  are  generally 


174        ROCK  EXCAVATION— METHODS  AND  COST. 

heaped  full  with  dippers,  so  a  car  holds  not  less  than  3  cu. 
yds.  of  loose  material.  Each  shovel  is  served  by  two  dinkey 
engines  hauling  trains  of  six  cars.  The  wages  paid  per  10- 
hr.  day  are  low,  being  as  follows :  i  shovel  engineer,  $3 ; 
i  craneman,  $2;  i  fireman,  $1.25;  4  pit  laborers,  $i  each;  2 
dinkey  engineers,  $1.75  each;  i  superintendent  (to  two 
shovels),  $5.  There  are  no  firemen  or  brakemen  on  the 
trains.  The  grade  from  the  shovels  to1  the  dump  is  about  2 
per  cent,  in  favor  of  the  load.  The  following  was  the  cost 
of  operating  two  shovels  one  month  in  1903.  Shovel  No.  i 
worked  171  hrs. ;  No.  2  worked  161  hrs. : 

No.  i.  Excav.  5,513  carloads,  wages   $287.65 

Transporting  5,513  carloads,  500  ft. 

haul  (one  way),  wages  83.60 

Drilling  272  ft.  at  4  cts 10.88 

Explosives 27-52 

No.  2.  Excav.  3,362  carloads,  wages $243.01 

Transporting   3,362   carloads,    1,500 

ft.  haul  (one  way),  wages 60.13 

Drilling  239  ft.  at  4  cts 9.56 

Explosives     27.80 

Dumping,  8,875  carloads   142.27 

Track  work    267.60 

Trackwork  (nights)    75-^7 

Blacksmith  work   76.30 

Repair  "       1 10.23 

Carpenter  shop    37-7° 

Renewal  and  repair  supplies  J96-39 

Coal  for  shovel  No.  i  at  $4.50  ton 77-3° 

"     "        "     No.  2    "       "      "    72.70 

Coal  for  4  dinkeys 91.00 

Iron 23.85 

Lumber   37.39 

Oil    25.27 

Waste  .QO 


Total  for  8,875  carloads $1,984.92 


COST   OF  LOADING   AND   TRANSPORTING.         175 

When   washed,  these  8,875   carloads  yielded  7,633  tons 
of  ore. 

In  1902  during  a  month  of  201  hrs.  the  two  shovels  dug 
10,703  carloads,  at  the  following  cost: 

Excavating,  wages    $5334J 

Hauling,  wages    250.40 

Drilling,  812  ft.,  at  /  cts 32.48 

Explosives 97-37 

Dumping *94-99 

Blacksmith  work   84.11 

Carpenter       "       56.40 

Repair  "       137.28 

Track  "       185.10 

Extra  (night)  labor  73-3° 

Renewal  and  repair  supplies  182.46 

Fuel   247.40 

Iron,  $24.60 ;  lumber,  $29.23    53.83 

Oil,  $28.40 ;  waste,  $2.28 30.68 


Total  for  10,703  carloads $2,159.21 

When  washed  these  10,703  carloads  yielded  7,573  tons  of 
ore. 

Wages  of  shovel  crew  are :  I  shovel  engineer,  $3 ;  I  crane- 
man,  $2;  i  fireman,  $1.25;  4  laborers  at  $i ;  2  dinkey  en- 
gineers at  $1.75;  J/2  superintendant  at  $5.  There  were  no 
firemen  nor  brakemen  on  the  trains.  Grade  from  shovel  to 
dump,  2  per  cent,  in  favor  of  loaded  trains. 

The  best  day's  work  with  one  shovel  was  Jan.  30,  1903. 
The  work  was  in  a  side-cut,  25  ft.  high  and  cost  as  follows : 

Excavating  (441  carloads),  wages $12.75 

Hauling  (400  ft.  one  way),  wages 3.50 

Drilling  23  ft.  at  4  cts 92 

Explosives 1.66 

Dumping 4.50 

Trackwork    18.00 

.  Blacksmith  work   3.08 


176        ROCK  EXCAVATION— METHODS  AND  COST. 

Repair  work 5.15 

Carpenter  work   3.00 

Coal  at  $4.50  ton 5.45 

Iron  and  lumber   3.00 

Waste    83 


Total  for  441  carloads   $61.84 

When  washed  these  441  carloads  yielded  450  tons  of  ore. 
For  the  sake  of  comparison  the  following  hand  work  in 
this  ore  will  be  interesting : 

Loaders  received  8  cts.  per  cu.  yd.  and  earned  $1.25  to 
$2  a  day;  common  laborers  received  10  cts.  per  hr.  In  a 
month  of  235  working  hours,  with  a  haul  of  800  ft.  (one 
way),  600  ft.  being  a  mule  haul  and  200  ft.  by  gravity,  in  a 
material  not  as  hard  as  hardpan,  and  working  to  a  face  16 
ft.  high,  the  cost  was  as  follows : 

Digging  2,272  carloads  =  4,544  cu.  yds.  .  .$363.52 
Hauling     "  ,  800  ft.  one  way  .  .     67.89 

Drilling  273  ft.  at  4  cts.  .  . 10.92 

Explosives    36-67 

Dumping 32.59 

Repair  and  trackwork    40.68 

Blacksmith  work   3.10 

Iron,  $2 ;  lumber,  $2.62   4.62 

Oil,  $2.75 ;  waste,  $0.18  2.93 

Foreman  ( i  mo.)    62.50 


Total  for  2,272  carloads $625.42 

When  washed,  these  2,272  carloads  yielded  2,488  tons  of 
ore.  These  cars  were  smaller  than  the  cars  hauled  by  the 
engines,  and  they  held  2  cu.  yds.  of  loose  material. 

Cost  by  Wheelbarrows. — A  wheelbarrow  load  averages 
about  1/2B  cu.  yd.  of  solid  rock.  A  man  will  load  such  a 
barrow  in  2  mins.,  and  will  walk  with  it  at  a  speed  of  180 
ft.  per  min.  if  he  is  lazy  and  to  250  ft.  per  min.  if  he  is 
active;  and  he  will  lose  %  mm-  each  trip  in  dumping  the 


COST   OF  LOADING   AND    TRANSPORTING.         177 

barrow,  fixing  run  planks,  etc.  Assuming  a  speed  of  200 
ft.  per  min.  and  wages  15  cts.  per  hour,  the  cost  of  loading, 
hauling  and  dumping  is : 

Rule  I.  To  a  fixed  cost  of  18  cts.  per  cu.  yd.  of  solid  rock 
add  6%  cts.  per  cu.  yd.  per  100  ft.  of  one-way  haul  from 
pit  to  dump.* 

Cost  of  Hauling  in  Carts  and  Wagons. — Since  a  cubic  yard 
of  loose,  broken  stone  weighs  about  as  much  as  a  cubic  yard 
of  earth  measured  in  place ;  and  since,  ordinarily,  I  cu.  yd. 
of  solid  rock  becomes  1.7  cu.  yds.  when  broken,  we  may  say 
that  a  team  will  haul  about  60  per  cent,  as  many  cubic  yards 
of  solid  rock  per  day  as  of  earth.  In  other  words,  if  the 
roads  are  such  that  I  cu.  yd.  of  packed  (not  loose)  earth 
would  make  a  fair  wagon  load  for  two  horses,  then  0.6  cu. 
yd.  of  solid  rock  would  be  a  fair  load.  In  my  book  on  earth- 
work I  have  discussed  in  considerable  detail  the  sizes  of 
loads  of  earth  that  teams  can  haul,  and  it  is  only  necessary 
to  multiply  the  earth  load  as  given  there  by  6/io  (or  60  per 
cent.)  to  find  the  equivalent  load  of  solid  rock.  Another 
way  to  estimate  loads  is  to  use  the  ton  of  2,000  Ibs.  as  the 
unit.  Solid  rock  seldom  weighs  more  than  2.2  tons  per  cu. 
yd.  Over  poor  earth  roads,  with  occasional  steep  pitches, 
a  load  of  I  ton  is  practically  all  that  an  ordinary  team  should 
be  counted  upon  to  haul,  or  less  than  l/2  cu.  yd.  of  solid 
rock.  If  the  road  is  hard  and  level,  a  team  will  haul  I  cu. 
yd.  of  solid  rock ;  or  one  horse  will  haul  l/2  cu.  yd.  in  a  cart. 
If  the  road  is  a  good  macadam  all  the  way,  with  no  grades 
over  4  per  cent.,  and  no  pulls  through  soft  earth,  a  good 
team  can  haul  about  1^/2  cu.  yds.  of  solid  rock,  but  these 
conditions  are  exceptional.  In  ordinary  city  and  village 
work,  and  on  level  hauls  over  hard  earth  roads,  assume  I 
cu.  yd.  of  solid  rock  as  a  load  for  two  horses.  A  team  travels 

*  In  this  rule,  and  in  the  rules  that  follow,  I  have  given  not  the  lowest  records 
of  cost  that  I  have,  as  will  be  seen  by  anyone  who  takes  the  pains  to  study  this 
book  well.  I  have  preferred  to  give  conservative  estimates  of  cost  in  all  the 
rules.  It  is  never  safe  to  estimate  too  closely  before  work  has  been  actually 
begun;  but  once  it  is  under  way  every  cent  per  yard  should  be  looked  after  with 
the  greatest  diligence.  In  a  word,  make  your  saving  in  your  work  and  not  in 
your  preliminary  estimate. 


i;8        ROCK  EXCAVATION— METHODS  AND  COST. 

220  ft.  per  min.,  or  2,y2  miles  an  hour,  at  a  walk  over  ordi- 
nary earth  roads,  a  little  faster  over  good  pavements  and 
a  little  slower  over  soft  roads,  the  variations  from  this 
average  of  2*/2  miles  an  hour  being  seldom  more  than  20 
per  cent.,  making  it  about  2  miles  an  hour  over  poor  roads 
to  3  miles  an  hour  over  the  best  macadamized  roads.  It  is 
perfectly  safe  to  say  that  a  team  can  walk  steadily  for  8  hrs., 
averaging  the  speeds  above  given,  going  loaded  and  return- 
ing empty ;  so  if  the  shift  is  10  hrs.  long,  and  not  over  2  hrs. 
are  lost  in  loading  and  dumping,  the  team  has  8  hrs.  to 
travel,  in  which  time  it  will  cover  16  miles  over  poor  earth 
roads,  24  miles  over  good  macadamized  roads  and  20  miles 
over  ordinary  earth  roads.  If  the  hauls  are  short  it  may 
happen  that  so  much  time  is  lost  in  loading  and  dumping 
that  the  team  has  considerably  less  than  8  hrs.  of  actual 
walking  time  left.  Each  case  must  be  considered  by  the  con- 
tractor. 

As  to  the  wagons  used  for  hauling  one  and  two-man  stone, 
my  own  preference  is  for  an  ordinary  wagon  from  which 
the  box  has  been  removed  and  replaced  by  a  "stone  rack." 
A  stone  rack  is  3  ft.  wide  and  1 1  ft.  long,  its  floor  being  3-in. 
plank  and  its  sides  and  ends  nothing  but  3  x  4-in.  strips. 
This  makes  a  "box"  that  is  low  and  easily  loaded,  when 
necessary  big  stones  being  rolled  up  an  inclined  plank  onto 
the  wagon.  It  is  also  unloaded  easily,  large  stones  being 
simply  rolled  off  without  lifting.  Where  hauls  are  very 
short,  and  the  stone  all  broken  to  one-man  size,  a  patent 
dump  wagon  may  be  used  advantageously ;  but  such  a  wagon 
always  weighs  much  more  than  the  common  wagon  with  a 
stone  rack,  aside  from  the  fact  that  a  patent  dump  wagon  is 
always  harder  to  load.  As  above  stated,  a  driver  will  un- 
load I  cu.  yd.  solid  measure  (or  1.7  cu.  yds.  loose  measure) 
of  stone  from  a  stone  rack  in  7  mins.  if  he  is  vigorous  in 
his  work.  Certainly  two  men  should  never  take  more  than 
7  mins.  Two  men  and  the  driver  can  readily  load  I  cu.  yd. 
onto  a  stone  rack  in  15  mins.,  no  stone  being  heavier  than 


COST   OF  LOADING  AND    TRANSPORTING.         179 

two  men  can  lift.  Then  if  one  man  and  the  driver  unload 
in  7  mins.,  we  have  22  mins.  team  time  lost  in  loading  and 
unloading,  which  is  equivalent  to  12  cts.  per  cu.  yd.  (team 
and  driver  being  worth  35  cts.  an  hour),  8  cts.  being  for 
lost  team  time  loading  and  4  cts.  for  lost  time  dumping.  If, 
including  rests,  each  laborer  (exclusive  of  the  driver),  aver- 
ages jY-2  cu.  yds.  loaded  in  10  hrs.,  and  wages  are  15  cts.  an 
hour,  we  have  20  cts.  per  cu.  yd.  for  loading.  If  one  man, 
assisted  by  the  driver  of  each  team,  does  the  unloading,  the 
cost  of  his  help  need  not  exceed  3  cts.  per  cu.  yd.  We  have, 
therefore,  a  total  fixed  cost  of,  8  cts.  lost  team  and  driver 
time  loading,  plus  4  cts.  ditto  unloading,  plus  20  cts.  for 
labor  loading,  plus  3  cts.  for  helper  unloading,  making  a 
total  fixed  cost  of  35  cts.  per  cu.  yd.  of  solid  rock.  Our 
rule  for  loading  and  hauling  and  dumping  I  cu.  yd.  of  solid 
rock  (2.2  tons)  in  wagons,  under  the  above  conditions,  is: 

Rule  II.  To  a  fixed  cost  of  35  cts.  for  lost  team  time,  and 
labor  of  loading  and  dumping,  add  6/10  ct.  per  cu.  yd.  per 
100  ft.  of  haul  (one  way)  from  quarry  to  dump,  or  32  cts. 
per  mile  one  way ;  but  if  the  roads  are  such  that  y2  cu.  yd. 
of  solid  rock  (i.i  tons)  makes  a  load,  to  the  35  cts.  fixed 
cost  add  i  2/10  cts.  per  cu.  yd.  per  100  ft.  of  one-way  haul, 
or  64  cts.  per  mile.  By  using  extra  wagons,  as  should  be 
done  where  the  haul  is  so  short  that  a  team  cannot  be  kept 
on  the  walk  8  hrs. ;  or  by  using  more  men  loading  and  un- 
loading, as  should  be  done  when  the  hauls  are  very  short, 
the  fixed  cost  can  be  reduced  to  30  cts.  per  cu.  yd. 

In  railroad  work  one  driver  usually  attends  to  two  one- 
horse  dump  carts ;  and  as  rock  cuts  are  usually  higher  than 
the  dump  the  haul  is  down  hill,  so  that,  considering  the 
rough  roads,  big  loads  can  be  handled.  By  having  4  or  5 
men  to  load  each  cart,  there  is  about  the  same  amount  of  lost 
team  time  per  cu.  yd.  of  rock  as  above  assumed  for  loading 
wagons,  or  8  cts.  per  cu.  yd. ;  the  cost  of  dumping  is  about 
2  cts.,  making  a  fixed  cost  for  the  two  horses  and  driver  of 
10  cts.  per  cu.  yd.,  to  which  add  20  cts.  for  loading  to  get 


i8o        ROCK  EXCAVATION— METHODS  AND  COST. 

the  total  fixed  cost  for  labor  and  teaming.  With  wages  at 
15  cts.  per  hr.  for  laborers  and  35  cts.  for  a  driver  and  two 
one-horse  carts,  the  rule  for  loading  and  hauling  by  carts, 
l/4  cu.  yd.  of  solid  rock  per  cart,  is : 

Rule  III.  To  a  fixed  cost  of  30  cts.  per  cu.  yd.  of  solid 
rock  add  i  2/10  cts.  per  100  ft.  of  one-way  haul.  Mr.  Daniel 
Hauer  states  (see  page  226)  that  he  has  found  1/3  cu.  yd.  of 
solid  rock  to  be  a  fair  average  of  the  size  of  one-horse  cart 
load  on  railroad  work,  but  my  own  records  show  ^4  cu-  yd- 
to  have  been  an  average,  and  I  have  preferred  to  err,  if  at 
all,  on  the  conservative  side. 

Where  carts  or  wagons  must  be  hauled  up  a  steep,  bad 
road,  it  will  often  pay  to  lay  either  a  plank  road,  or  to  lay 
steel  channel  beams  so  as  to  form  a  trackway.  This  last 
method  has  been  used  with  advantage  where  a  hoisting  en- 
gine was  placed  at  the  top  of  a  long  hill  to  relieve  the  teams 
of  the  work  of  hill  climbing.  A  boy  on  a  horse  can  readily 
drag  the  snatch  rope  back  down  the  hill.  In  the  far  West 
it  is  customary  for  three  or  more  teams  to  be  hitched  to  a 
train  of  two  or  more  wagons,  and,  when  a  steep  hill  is  to  be 
ascended,  only  one  wagon  is  hauled  up  at  a  time.  On  long 
hauls  this  method  could  be  used  to  advantage  much  oftener 
than  it  is  in  the  East.  Snatch  teams  are  not  used  as  often 
as  they  should  be  to  enable  large  loads  to  be  handled  over  bad 
spots  in  the  road.  Where  the  roads  are  fairly  good  all  the 
year,  traction  engines  are  economic. 

For  hauling  cut  stone  in  large  blocks,  "stone  trucks"  are 
used.  A  stone  truck  is  a  strong  wagon  provided  with  a  plat- 
form which  hangs  below  the  hubs  of  the  wheels,  instead  of 
above  them,  as  in  the  ordinary  wagon. 

Where  large  derricks  are  available  at  both  ends  of  the 
haul,  wagon  boxes  can  be  made  so  as  to  be  lifted  off  by  the 
derricks,  both  for  loading  and  dumping  the  rock. 

Hauling  on  Stone-Boats. — For  moving  large  stones  a  short 
distance  stone-boats  or  sleds  are  often  used.  A  stone-boat 
is  a  flat  platform,  ordinarily  about  2^2  x  4  ft.,  on  wooden 


COST  OF  LOADING   AND    TRANSPORTING.         181 

runners  shod  with  iron.  It  possesses  three  advantages  over 
a  wheeled  vehicle :  First,  it  is  so  low  that  a  large  rock  can 
be  rolled  by  hand,  or  dragged  by  the  team  on  to  it;  second, 
it  cuts  no  ruts  into  wet  ground,  and,  third,  it  can  be  dragged 
about  in  narrow  places.  Obviously  a  team  cannot  haul  a 
very  large  load  very,  far  on  a  stone-boat,  but  surprisingly 
large  loads  can  be  hauled  a  short  distance  if  the  team  has 
long  rests  between  loads.  A  team  of  horses  weighing  2,400 
Ibs.  can  exert  a  pull  of  about  1,000  Ibs.  for  a  short  time  if 
they  have  a  good  earth  foothold.  The  sliding  friction  of 
iron  or  wood  on  earth  is  about  50  per  cent,  the  weight  of 
the  load  that  is  being  dragged ;  hence  a  team  is  capable  of 
dragging  a  stone-boat  and  load  together  weighing  2,000 
Ibs.  A  team  doing  such  heavy  work  could  probably  not 
average  more  than  2  hrs.  of  actual  pulling  per  day.  In 
stone-boat  work,  however,  a  stone  weighing  more  than  1,100 
Ibs.  (y$  cu.  yd.  solid)  is  seldom  handled.  Where  many  such 
stones  are  to  be  hauled  a  considerable  distance,  as  in  boulder 
quarrying,  I  have  found  it  an  excellent  plan  to  build  "skid 
roads."  A  skid  road  is  really  a  rough  railroad  without  the 
rails,  for  it  is  made  by  partly  bedding  in  the  ground  round 
sticks  of  unsawed  timber,  like  ties  for  a  railway  track,  3  to  6 
ft.  apart.  A  stone  boat  with  wooden  runners,  8  to  12  ft. 
long,  can  be  "skidded"  or  hauled  along  over  these  ties  with 
surprising  ease  if  the  ties  are  kept  well  greased.  Indeed,  a 
team  can  thus  pull  a  bigger  load  than  with  a  wagon  wherever 
there  is  not  a  well  made  road.  Where  growing  timber  is 
at  hand  a  skid  road  may  be  made  at  less  cost  than  grading 
a  wagon  road,  and  it  possesses  the  inestimable  value  of 
being  a  good  road  even  in  wet  weather.  I  have  seen  wagons 
that  were  dragged  with  difficulty  through  the  mud  when  the 
load  was  less  than  y%  cu.  yd.  of  solid  rock  (550  Ibs.)  ;  and 
it  often  happens  in  the  fall  and  spring  of  the  year  that  % 
cu.  yd.  of  solid  rock  is  a  big  load  for  wagons  traveling  over 
earth  roads  badly  rutted  and  muddy.  In  such  cases  a  skid 
road  can  often  be  built  to  advantage. 


182        ROCK  EXCAVATION— METHODS  AND  COST. 

Cost  by  Dump  Cars. — For  a  discussion  of  the  tractive 
power  of  horses  and  the  rolling  resistance  of  cars,  the  reader 
is  referred  to  my  book  on  earthwork.  On  a  level  track  a 
team  will  readily  haul  two  dump  cars  loaded  with  3  cu.  yds. 
of  solid  rock  over  the  ordinary  narrow-gauge  track  with 
light  rails.  In  railroad  work  the  grade  is  usually  in  favor 
of  the  load  from  cut  to  fill,  and  it  is  safe  to  assume  that  one 
horse  will  haul  two  dump  cars  (i^-yd.  body)  loaded  with 
y2  cu.  yd.  solid  rock  in  each  car;  with  a  well  kept  track 
slightly  in  favor  of  the  load,  but  not  so  steep  as  to  stall  the 
horse  returning  with  the  empty  cars,  it  is  safe  to  count  upon 
Y^  cu.  yd.  in  each  of  the  two  cars. 

In  a  thorough  cut  the  track  is  usually  laid  Y-fashion,  the 
two  branches  of  the  Y  being  carried  up  close  to  the  rock 
face.  Two  empty  cars  are  left  on  one  branch  of  the  Y  to 
be  loaded  while  the  two  loaded  cars  are  hauled  away  from 
the  other  branch.  If  the  haul  is  short  and  only  a  few  loaders 
are  at  work,  only  one  car  is  hauled  at  a  time.  If  the  cut 
is  wide  enough,  and  it  often  is,  I  prefer  to  lay  two  parallel 
tracks  and  have  two  Y's,  for  in  that  way  the  loaders  need 
not  take  so  many  steps  to  get  a  stone  into  a  car,  since  there 
are  four  places  at  the  face  where  cars  may  stand,  instead 
of  two.  In  estimating  the  cost  of  loading  and  hauling  in 
cars,  using  horses  or  mules,  assuming  the  rock  to  be  broken 
up  into  sizes  that  one  or  two  men  can  lift,  it  is  never  safe 
to  count  upon  more  than  7^2  cu.  yds.  solid  rock  loaded  per 
man  in  10  hrs.,  and  often  it  will  be  wise  to  estimate  on  not 
more  than  6  cu.  yds.  With  wages  at  15  cts.  per  hr.,  the  load- 
ing costs  20  to  25  cts.  per  cu.  yd.  Assuming  i  cu.  yd.  of 
solid  rock  as  a  fair  load  for  one  horse  to  haul  in  cars ;  as- 
suming 4  mins.  lost  time  in  changing  from  the  empty  to 
the  loaded  cars  and  in  dumping ;  assuming  a  speed  of  200  ft. 
per  min.,  and  assuming  wages  of  driver  and  one  horse  at  25 
cts.  per  hr.,  we  have  I  %o  cts.  per  cu.  yd.  chargeable  to  lost 
time  at  pit  and  dump,  plus  J/£  ct.  per  cu.  yd.  per  100  ft.  of 
haul  (measured  one  way).  The  cost  of  dumping  is  largely 


COST   OF  LOADING  AND    TRANSPORTING.         183 

a  matter  of  how  many  yards  are  delivered  per  day  at  the 
dump.  However,  with  wages  at  15  cts.  an  hour,  the  cost  of 
dumping  is  seldom  less  than  2  cts.,  and  it  may  run  as  high 
as  5  cts.  per  cu.  yd.  Assuming  5  cts.  as  a  fair  average  of 
the  combined  cost  of  dumping  and  lost  team  time,  and  20 
cts.  as  the  cost  of  loading  by  hand,  we  have : 

Rule  III.  For  loading  and  hauling  with  dump  cars,  to  a 
fixed  cost  of  25  cts.  per  cu.  yd.  of  solid  rock,  add  y2  ct.  per 
cu.  yd.  per  100  ft.  of  one-way  haul. 

If  the  distance  is  great  enough  to  warrant  the  use  of  a 
team  of  horses  instead  of  one  horse,  the  cost  of  hauling  will 
be  V3  ct.  per  cu.  yd.  per  100  ft.,  if  wages  of  team  and  driver 
are  35  cts.  per  cu.  yd.  I  estimate  the  cost  of  track  laying  at 
$100  per  mile,  of  wear  and  tear  on  ties  at  another  $100,  and 
of  pulling  up  track  at  $50,  making  a  total  of  $250  per  mile, 
or  $5  per  100  ft.  of  track.  Dump  cars  can  be  estimated  as 
costing  about  $50  each,  3O-lb.  rails  at  $30  a  ton  and  ties 
(6x6  ins.  x  5  ft.)  at  25  cts.  each. 


CHAPTER  XL 
QUARRYING   STONE. 

General  Considerations. — In  this  chapter  the  quarrying  of 
stone  for  masonry  (other  than  concrete)  will  be  discussed. 
Stone  that  is  quarried  and  split  with  plug  and  feathers,  or 
otherwise,  to  dimensions  (ready  for  stone  cutters  to  begin 
dressing  the  surface)  is  called  dimension  stone.  If  it  is  quar- 
ried out  in  rough  slabs  or  blocks  of  irregular  dimensions  it 
is  called  rubble  stone,  or  backing  stone. 

In  quarrying  dimension  stone  the  first  step  is  to  secure 
a  working  face  in  the  quarry ;  the  next"  step  is  usually  to  cut 
or  blast  a  channel  at  each  end  of  this  face,  so  as  to  expose 
three  free  faces.  Then  it  is  possible,  by  wedging  or  blast- 
ing, to  loosen  a  long  block  of  stone  which  can  be  split  into 
short  blocks  that  can  be  handled  by  derricks.  Where  there 
is  a  good  market  for  rubble  stone,  it  is  not  customary  to 
make  end  channels,  but  merely  to  shake  up  the  rock  for  a 
short  distance  back  of  the  face  by  light  blasts,  and,  if  it  is 
a  sedimentary  rock,  large  irregular  slabs  can  be  barred  and 
wedged  out.  These  slabs  can  then  be  squared  up  by  sledg- 
ing or  by  plug  and  feathering,  or  both.  Obviously  this 
method  produces  a  very  considerable  amount  of  rubble 
stone,  but  it  is  the  common  method  in  small'  dimension  stone 
quarries. 

While  in  the  first  chapter  attention  was  called  to  the  joints 
that  exist  in  stone,  it  is  well  to  add  certain  facts  to  those  al- 
ready given,  for  the  art  of  quarrying  is  largely  the  art  of 
taking  advantage  of  joints  and  natural  cleavage  planes. 
Granite,  which  to  the  ordinary  eye  appears  massive  and 
without  planes  of  natural  cleavage,  has  in  fact  a  "rift"  clear- 
ly seen  by  the  trained  eye.  Along  this  "rift"  it  may  be  split 
with  comparative  ease.  At  right  angles  or  perpendicular  to 

184 


QUARRYING   STONE.  185 

the  "rift"  in  one  direction  are  planes  of  cleavage,  called  the 
"grain,"  along  which  the  stone  splits  with  less  ease;  while 
at  right  angles  to  the  "rift"  in  the  other  direction  are  planes 
of  natural  cleavage,  called  the  "head,"  along  which  it  is  still 
possible  to  split  the  stone,  but  with  less  ease  than  along  the 
"grain"  or  along  the  "rift."  These  three  planes  of  cleavage 
are  shown  in  Fig.  18.  All  sedimentary  rocks  have  a  "rift" 
which  corresponds  with  the  planes  of  stratification  or  beds ; 
but  the  trap  rocks,  like  diabase,  diorite,  porphyry,  etc.,  often 
have  no  rift  at  all,  and  are  consequently  unfit  for  use  as  di- 
mension stone,  since  when  hammered  or  wedged  they  are 
apt  to  split,  like  glass,  irregularly. 


ffift- 

rfl 


Grain 


H< 


The  cost  of  quarrying  stratified  rocks,  like  sandstone  and 
limestone,  depends  largely  upon  two  factors:  First,  the 
thickness  of  the  beds,  and,  second,  the  "dip"  of  the  beds. 
The  "dip"  is  the  angle,  or  slope,  that  the  bed  makes  with  a 
horizontal  plane.  If  the  beds  lie  horizontally,  just  as  when 
they  were  originally  deposited  in  the  primaeval  sea,  the  stone 
is  quarried  out  in  successive  layers ;  and,  as  these  layers 
usually  vary  in  thickness,  the  quarryman,  after  the  quarry 
has  been  well  opened,  can  select  a  layer  of  thickness  to  suit 
the  demand  of  any  particular  purchaser.  If  the  beds  dip  at 
a  steep  slope  into  the  earth,  the  quarryman  must  usually  re- 
move thick-bedded  and  thin-bedded  stone,  all  together,  as 
he  goes  down ;  and  besides  he  must  abandon  his  quarry,  or 
resort  to  mining  methods,  before  a  very  great  depth  has 
been  reached,  because  it  will  not  pay  to  remove  the  increas- 
ingly large  amount  of  stripping.  On  the  other  hand,  where 


i86        ROCK  EXCAVATION— METHODS  AND  COST. 

the  beds  dip  at  a  high  angle  the  quarryman  can  determine, 
by  examining  the  exposed  outcrop,  what  the  thickness  of 
each  bed  is,  and  can  count  with  some  certainty  upon  the 
character  of  each  bed.  Where  the  beds  lie  flat,  the  thin 
beds  are  usually  on  top,  and  thicker  beds  exist  below ;  but 
this  is  not  always  the  case,  and  to  determine  the  character 
of  the  deposit  diamond  drill  cores  should  be  obtained. 

If  the  beds  of  stratified  rock  are  quite  thin,  the  stone  may 
be  fit  for  flagstone,  curbing,  lintels,  paving  blocks,  slope  wall 
stone,  basement  masonry  and  the  like ;  but  will  of  course  be 
valueless  for  heavy,  architectural  masonry  or  for  engineer- 
ing masonry  where  specifications  call  for  thick  courses.  This 
simple  fact  is  frequently  overlooked  by  engineers  in  draw- 
ing masonry  specifications,  and  they  often  call  for  thick- 
nesses of  courses  that  either  are  not  to  be  found  in  local 
quarries  at  all,  or,  if  found,  are  quarried  only  at  great  ex- 
pense by  first  removing  a  lot  of  thin  bedded  stone  overlying 
the  thicker  beds  required.  Times  without  number  I  have 
seen  evidences  of  such  ignorance  of  quarry  products  and 
quarrying  costs  that  obvious  as  these  facts  seem  I  deem  them 
worthy  of  emphasis.  If  the  beds  of  stratified  rock  are  thick- 
er than  the  courses  of  masonry  specified,  then  the  quarried 
blocks  must  be  split  at  a  cost  that  should  never  be  overlooked 
by  the  quarryman  or  the  contractor  in  estimating  a  fair 
price  for  his  product.  Thus  it  appears  that  there  is  a  happy 
medium  as  regards  the  economic  thickness  of  beds. 

Joints. — All  rocks,  whether  igneous  or  sedimentary,  con- 
tain "joints,"  or  seams  that  run  through  the  natural  beds. 
Often  these  "joints"  are  clearly  visible,  but  at  times  the 
split  may  be  so  thin  as  to  be  invisible  except  to  the  expert 
eye.  In  stratified  rock  the  "joints"  as  a  rule  are  perpen- 
dicular to  the  planes  of  bedding,  and  are  spaced  quite  regu- 
larly, as  if  a  giant  quarryman  had  struck  the  rock  with  a 
sledge  at  intervals,  cracking  it  in  vertical  planes.  The  joints 
in  stratified  rock  have,  as  a  rule,  two  dominant  trends,  one 
set  of  joints  being  parallel  with  the  "dip"  ("dip  or  end 


QUARRYING   STONE.  187 

joints")  and  the  other  set  at  right  angles,  or  parallel  with 
the  "strike"  ("strike  or  back  joints"). 

In  granites  and  traps  the  "joints"  occur  at  irregular  in- 
tervals and  often  intersect  at  varying  angles ;.  nevertheless 
there  are  generally  two  sets  of  vertical  joints  intersecting 
approximately  at  right  angles,  and  frequently  there  is  a  third 
set  of  horizontal  or  "bottom  joints."  If  the  joints  are  close 
together  it  will,  of  course,  be  impossible  to  quarry  building 
blocks;  though,  on  the  other  hand,  the  quarrying  of  stone 
to  be  crushed/ for  concrete  or  macadam  is  greatly  facilitated 
by  numerous  joints,  as  exemplified  in  the  trap  rocks  of  the 
Hudson  River.  Joints  are  usually  quite  conspicuous  near 
the  surface,  due  to  the  fact  that  changes  of  temperature 
have  opened  them,  and  solutions  of  iron  salts  passing 
through  the  joints  have  stained  the  rock.  But  wherever 
granite  is  found  with  numerous  close  joints  in  the  surface 
beds,  it  may  be  inferred  that  similar  joints  exist  in  the  lower 
beds  even  if  they  are  invisible,  and  even  if  the  blocks  quar- 
ried from  the  lower  beds  appear  solid.  Merrill  cites  a  granite 
quarry  in  which  the  stone  at  a  depth  of  25  ft.  appeared  to 
be  perfectly  solid,  although  above  it  was  full  of  joints ;  but 
upon  polished  blocks  he  was  able  to  discover  fine  hairline 
joints  which  eventually  would  doubtless  open  up  upon  ex- 
posure. I  would  suggest  that  tests  on  the  tensile  strength  of 
diamond  drill  cores  would  quickly  prove  the  existence  or 
non-existence  of  such  joints. 

Where  joints  in  granite  run  verically  and  at  right  angles 
to  one  another,  as  well  as  horizontally,  the  quarry  is  known 
as  a  "block  quarry."  Where  there  are  practically  no  vertical 
joints,  but  where  a  series  of  nearly  horizontal  joints  divides 
the  granite  into  sheets  or  beds,  the  quarry  is  a  "sheet 
quarry."  The  beds  in  sheet  quarries  are  usually  lenticular 
in  shape,  thin  at  the  edges  and  thick  in  the  middle.  In  such 
a  quarry  blocks  10  ft.  thick  and  309  ft.  long  have  been 
loosened. 

Plug   and   Feathers. — Before    studying'  the    methods    of 


i88 


ROCK  EXCAVATION— METHODS  AND  COST. 


quarrying  it  is  necessary  to  understand  certain  of  the  com- 
moner tools  and  machines.  Among  these  the  most  impor- 
tant are  the  plug  and  feathers,  shown  in  Fig.  19.  These 
simple  tools  are  used  for  splitting  large  blocks  of  stone  into 
smaller  blocks  and  for  squaring  up  irregular  stones.  The 
plug  is  the  wedge,  and  the  feathers  are  merely  two  short 
pieces  of  half-round  iron  whose  curved  sides  fit  the  sides 
of  the  drill  hole,  while  their  flat  sides  receive  the  thrust  of 


Fig.  19 

the  plug.  It  is  astonishing  to  see  how  thick  a  block  of 
granite  may  be  split  with  so  small  and  simple  a  device.  To 
split  a  block  of  granite,  a  row  of  holes  about  ^  or  ^4  in- 
diam.  and  2^2  to  5  ins.  deep  are  drilled  about  6  to  8  ins. 
apart.  Then  a  pair  of,  feathers  and  a  plug  are  placed  in 
each  hole,  the  plugs  being  driven  home  with  light  blows  of 
a  hammer  until  all  are  tight.  Then  each  plug  in  succession 
is  struck  one  or  two  blows,  the  quarryman  telling  by  the 
ring  of  the  metal  under  the  blow  whether  the  strain  is  prac- 
tically the  same  in  each  wedge.  With  plug  holes  only  5  ins. 
deep  a  block  of  granite  6  ft.  thick  can  be  split,  leaving  a  face 
almost  as  flat  as  a  board.  For  granite  blocks  3  ft.  thick,  a 
hole  2.Y-2  or  3  ins.  deep  will  suffice.  Some  limestones  also 
break  remarkably  well  with  shallow  plug  holes,  but  marbles 


QUARRYING   STONE. 

and  sandstones  as  a  rule  require  deep  holes,  although  with 
some  sandstones  holes  iJ/£  ins.  x  8  ins.  will  break  a  sheet  4 
ft.  thick,  perfectly  true,  according  to  Saunders.  In  most 
sandstones,  however,  the  holes  are  usually  1^4  to  2  ins. 
diam.,  and,  as  a  general  rule,  of  a  depth  equal  to  2/s  the 
thickness  of  the  stone.  The  holes  are  spaced  4  to  16  ins. 
apart.  In  some  sandstones  the  plug  holes  must  be  drilled 
entirely  through  the  stone  to  insure  a  true  break.  The  plugs 
need  not  always  be  of  the  same  length  as  the  depth  of  the 
hole.  Sometimes  it  is  found  desirable  to  alternate  deep  and 
shallow  plug  holes  in  the  same  row.  In  this  case  the  lower 
half  of  the  deep  holes  may  be  drilled  with  a  smaller  bit,  so 
that  the  plugs  in  these  holes  will  strain  only  the  bottom  half 
of  the  stone. 

For  drilling  plug  holes  there  are  three  methods  in  com- 
mon use:  (i)  Drilling  by  hand;  (2)  drilling  with  a  pneu- 
matic hammer,  called  a  pneumatic  plug  drill;  and  (3)  drill- 
ing with  an  ordinary  rock  drill  mounted  on  a  quarry  bar. 
Since  plug  holes  in  granite  are  seldom  more  than  6  ins.  deep 
(usually  3  ins.),  either  hand  drilling  or  pneumatic  plug 
drilling  should  be  used ;  but  where  deeper  holes  must  be  put 
down  a  rock  drill  on  a  quarry  bar  should  be  used. 

Cost  of  Plug  Drilling  by  Hand. — By  timing  a  aumber  of 
masons  at  work  splitting  granite  blocks  24  to  30  ins.  thick, 
I  found  that  each  man  drilled  each  hole  ( ^-in.  diam.  x  2^2 
ins.  deep)  in  a  trifle  less  than  5  mins.,  by  striking  about  200 
blows ;  and  it  took  about  I  min.  for  placing  and  striking  each 
set  of  plug  and  feathers.  Blocks  30  ins.  long,  with  four 
plug  holes,  were  drilled  and  split  with  the  plugs  and  feath- 
ers in  24  mins.,  on  an  average.  At  this  rate,  a  good  work- 
man can  drill  and  plug  80  holes  in  8  hours. 

Cost  of  Pneumatic  Plug  Drilling. — For  drilling  plug  holes 
in  granite  certainly  no  tool  is  as  economic  as  the  pneumatic 
plug  drill.  Fig.  20  shows  one  of  these  drills  at  work  on 
the  Wachusett  Dam  granite  quarry.  It  will  be  seen  that 
horizontal  as  well  as  vertical  holes  can  be  drilled  rapidly, 


igo        ROCK  EXCAVATION— METHODS  AND  COST. 

which  in  itself  is  a  distinct  advantage  over  the  quarry  bar 
method.  The  plug  drill  shown  in  Fig.  20  does  not  rotate 
the  bit  automatically,  which  I  consider  a  positive  advantage 
since  it  simplifies  the  mechanism  and  reduces  the  wearing 
parts.  The  operator  turns  the  bit  with  a  wrench,  which  is 
such  light  work  as  to  add  little  to  his  expenditure  of  energy. 


Fig.  20. 

The  ordinary  plug  drill,  according  to  the  manufacturers, 
consumes  15  cu.  ft.  of  free  air  per  min.  at  70  Ibs.  pressure. 
At  the  Wachusett  Dam  I  found  that  a  workman  averaged 
one  hole.  («Hj-in.  diam.  x  3  ins.)  drilled  in  \y2  mins.,  in- 
cluding the  time  of  shifting  from  hole  to  hole,  but  not  in- 
cluding the  time  of  driving  the  plugs.  About  250  plug  holes 


QUARRYING   STONE.  igi 

are  counted  a  fair  day's  work  for  a  plug  drill  where  the 
driller  does  not  drive  the  plugs  himself. 

Not  only  for  plug  hole  drilling,  but  for  block-holing,  has 
the  pneumatic  drill  a  promising  future.  A  portable,  gaso- 
line-driven air  compressor,  such  as  is  commonly  used  for 
running  pneumatic  riveters,  would  serve  admirably  for  plug 
drilling  purposes  in  quarries  where  a  large  compressed  air 
plant  is  not  already  installed. 

The  Quarry  Bar. — A  quarry  bar  is  a  long  bar  mounted  on 
four  legs,  and  upon  the  bar  the  drill  is  mounted,  so  that  the 
drill  can  be  moved  quickly  from  hole  to  hole  along  the  bar, 


Fig.  21. 

or,  as  shown  in  Fig.  21,  the  stone  in  which  the  plug  holes 
are  being  drilled  can  be  moved  on  a  truck.  By  having 
wheels  with  perforated  holes  (Fig.  21)  the  drill  helper  can 
move  the  truck,  by  means  of  a  crow-bar,  just  far  enough 
for  drilling  the  next  hole.  It  is  stated  in  the  Ingersoll-Ser- 
geant  catalogue  that  in  a  granite  a  "Baby"  drill  on  a  quarry 
bar  will  drill  a  hole  3  or  4  ins.  deep  in  y$  min.,  and  it  can  be 
moved  and  started  in  another  hole  in  less  than  y^  min.,  so 
that  100  ft.  of  hole  are  drilled  in  a  day. 

The  quarry  bar  is  a  device  that  should  be  used  far  oftener 
than  it  is;  for  example,  wherever  vertical  drill  holes  aie 
spaced  close  together,  as  in  shallow,  open  cuts,  a  long  quarry 


192        ROCK  EXCAVATION— METHODS  AND  COST. 

bar  may  be  preferable  to  a  tripod,  because  of  the  time  saved 
in  setting  up.  In  trench  work  a  quarry  bar  might,  in  many 
cases,  be  used  to  advantage  with  the  bar  spanning  the  trench. 

Broaching. — In  quarrying  granite  the  quarry  bar  is  used 
to  some  extent  for  broach  channeling,  which  consists  in 
drilling  a  row  of  holes  close  together  like  the  holes  in  a 
postage  stamp  and  then  using  a  "broach,"  or  chisel,  to 
break  down  the  rock  between  the  holes.  The  wall  left  be- 
tween the  holes  is  ^4  to  2  ins.  thick,  depending  upon  the 
hardness  of  the  rock.  The  "broach"  is,  of  course,  not  ro- 
tated like  the  ordinary  drill  bit.  In  the  Ingersoll-Sergeant 
catalogue  the  following  data  are  given  as  to  average  broach 
channeling  work  done  per  day  by  one  drill  on  a  quarry  bar : 
In  granite,  10  to  20  sq.  ft.;  in  marble,  20  to  30;  in  lime- 
stone, 15  to  35 ;  in  sandstone,  20  to  40  sq.  ft. 

Where  it  is  necessary  to  excavate  igneous  rocks,  like 
granite  or  schist,  close  up  to  large  buildings  whose  founda- 
tions must  not  be  disturbed,  broach  channeling  is  often 
specified. 

In  this  connection  it  is  well  to  quote  from  Engineering 
Record,  Feb.  7,  1903,  a  method  of  blasting  close  to  a  tall 
brick  building  without  channeling.  The  rock  excavation 
was  60  ft.  deep,  the  rock  being  stratified  in  I  to  4-ft.  layers. 
A  trench  10  ft.  wide  was  taken  out  (lo-ft.  lifts)  parallel 
with  the  building.  Along  the  face  of  the  building  a  row  of 
holes  was  drilled  18  ft.  deep,  holes  being  6  to  8  ins.  center  to 
center.  A  second  parallel  row  of  holes  was  drilled  2  ft. 
away  from  the  first  row,  the  holes  being  2  ft.  apart  and 
loaded  lightly  with  40  per  cent,  dynamite.  The  holes  in  the 
row  next  to  the  building  were  not  charged,  but  the  blast 
caused,  the  rock  to  crack  along  the  line  of  these  uncharged 
holes. 

The  Gadder. — The  Ingersoll  gadder  is  a  machine  shown 
in  Fig.  22.  It  is  simply  an  ordinary  rock  drill  mounted  upon 
a  block  which  can  be  raised  or  lowered  on  an  upright  post. 
The  post  is  pivoted  at  its  lower  end  to  a  heavy  cast-iron  bed 


QUARRYING   STONE.  193 

plate  mounted  on  wheels.  The  machine  will  drill  holes  in 
a  horizontal  line  near  the  floor  of  the  quarry,  or  in  a  ver- 
tical row,  or  in  a  line  at  any  desired  angle,  for  the  post  can 
be  tilted  at  will.  After  drilling  the  holes,  plugs  and  feathers 
are  used  to  break  off  blocks  as  desired.  Fig.  22  shows  par- 
allel channels  made  with  a  channeler,  and  it  shows  the  plug 
and  feather  holes  made  with  the  gadder.  A  drill  is  said  to 
have  a  record  of  350  ft.  of  holes  in  10  hrs.  in  marble,  only 
1/3  min.  being  required  to  move  from  one  2- ft.  hole  and 
begin  drilling  the  next. 


Fig.  22. 

Channelers. — In  quarrying  sandstones  and  marbles,  chan- 
neling machines  are  largely  used;  and,  in  the  future,  chan- 
nelers  will  be  often  used  in  rock  excavation  where  it  is  de- 
sirable to  have  smooth  sides.  On  the  Chicago  Canal  exca- 
vation track  channelers  were  used.  Fig.  23  shows  a  Sul- 
livan channeler,  and  Fig.  24  shows  a  wheel  pit  extension, 
21  ft.  wide  and  185  ft.  deep,  made  with  Sullivan  channelers 
for  the  Cataract  Construction  Co.  at  Niagara  Falls.  It  will 
be  noticed  that  at  each  successive  lift  there  is  an  offset  or 
step  of  about  6  ins.,  but  that  by  giving  a  slight  batter  to  the 


194        ROCK  EXCAVATION— METHODS  AND  COST. 

wall  in  each  lift  the  trench  preserves  the  same  width  at  the 
bottom  as  at  the  top. 

A  track  channeler  is  a  self-propelling  machine  that  travels 
back  and  forth  on  a  10  to  3O-ft.  section  of  track  having  a 
gage  of  4  ft.  ii  ins.  The  channelers  used  on  the  Chicago 
Canal  weighed  about  11,000  Ibs.  each.  The  stroke  was  10 
ins.,  and  about  250  blows  were  struck  per  min.,  the  chan- 
neler moving  forward  a  fraction  of  an  inch  at  each  blow. 
The  gage  of  the  cutting  bit  was  2^  ins.  at  the  start,  and 
decreased  in  width  by  %  in.  each  2  ft.,  as  in  drilling.  The 
extreme  depth  of  a  lift  was  14  ft.  The  channels  cut  were 
perfectly  vertical.  Channelers  are  made  that  will  cut  up  an 


Fig.  23. 

angle  of  45°  for  use  in  quarries  where  the  strata  have  a 
sharp  dip.  Channelers  are  also  made  to  be  mounted  on  quarry 
bars,  the  catalogues  of  makers  showing  a  variety  of  types 
and  sizes.  Manufacturers  state  that  a  25  to  30  H.-P.  boiler 
will  run  a  channeler  having  a  6l/2  to  7-in.  cylinder,  or  that 
300  to  350  cu.  ft.  of  free  air  per  min.  at  80  Ibs.  pressure  will 


QUARRYING   STONE.  195 

be  consumed.    A  re-heater  is  generally  mounted  in  place  of 
the  boiler  when  compressed  air  is  used. 

The  following  data  are  given  in  the  Ingersoll-Sergeant 
catalogue  as  being  conservative  estimates  based  upon  actual 
monthly  averages.  The  number  of  square  feet  channeled 
per  day :  75  sq.  ft.  of  hard  brownstone  or  sandstone ; 
75  to  150  sq.  ft.  of  marble ;  200  sq.  ft.  of  soft  Lake  Superior 
browstone ;  250  sq.  ft.  of  soft  oolitic  limestone.  The  actual 


Fig.  24. 

averages  on  the  Chicago  Drainage  Canal  work  are  given  in 
Chapter  XIII.,  where  also  are  given  reliable  data  of  cost. 
It  requires  two  men  and  about  l/2  ton  of  coal  per  day  to  run 
a  channeler — in  fact,  the  cost  of  operating  is  practically  the 
same  as  for  a  steam  drill. 

It  does  not  pay  to  use  track  channelers  for  quarrying 
granite,  since  broach  channeling  in  granite  is  cheaper. 

For  quarrying  large  dimension  stones  (granite  excepted) 
the  channeler  has  become  an  economic  necessity.  Its  first 


196       ROCK  EXCAVATION— METHODS  AND,  COST. 

cost  should  not  prevent  its  purchase,  once  the  quarry  has 
been  opened  sufficiently  to  prove  the  marketability  of  the 
stone.  A  channeler  will  quickly  save  its  cost  in  the  better 
price  received  for  the  stone  and  in  the  saving  on  freight. 
The  last  item  is  one  often  overlooked,  but  it  may  be  said, 
roughly  speaking,  that  fully  20  per  cent,  of  the  stone  quar- 
ried without  channeling  is  lost  in  the  subsequent  cutting  and 
dressing  after  reaching  its  destination.  Since  rough  di- 
mension stone  is  paid  for  by  its  neat  measurement,  it  is  evi- 
dent that  in  the  end  the  quarryman  must  foot  the  bill  for 
this  waste  and  the  freight  upon  it.  The  actual  cost  of  chan- 
neling when  computed  in  cents  per  cubic  foot  of  stone  is 
really  slight ;  for  the  stone  is  not  cut  up  with  the  channeler 
into  merchantable  blocks,  like  harvesting  ice,  but  a  series  of 
parallel  channels  are  cut  across  the  quarry  so  as  to  loosen 
blocks  of  stone  which  may  be  50  ft.  or  more  in  length.  These 
long  blocks  are  then  split  with  plug  and  feathers  into  sizes 
that  the  derricks  can  handle.  The  smaller  blocks  are  then 
either  sawed  up,  or  still  further  reduced  in  size  by  plug 
and  feathering.  If  the  channels  are  9  ft.  apart,  each  square 
foot  of  channel  releases  9  cu.  ft.  of  stone,  so  that  if  the  cost 
of  channeling  is  9  cts.  per  sq.  ft.,  the  cost  per  cubic  foot  is 
i  ct. 

In  dimension  stone  quarries  very  large  guy  derricks  are 
used,  so  that  it  is  possible  to  handle  blocks  of  stone  weighing 
20  tons.  The  following  paragraph  gives  the  cost  of  one  of 
these  huge  derricks:  ^ 

Cost  of  a  Quarry  Derrick. — Saunders  gives  the  following 
cost  data  in  the  magazine,  Stone  (New  York),  1890,  p.  95: 
A  large  quarry  derrick  capable  of  lifting  20  tons  with  a 
single  line,  having  a  24  x  24-in.  mast,  75  ft.  high,  and  a  65- 
ft.  boom  actually  cost  as  follows: 

Timber  for  mast  $45-OO 

Timber  for  boom 28.00 

Expense  of  delivering  timber 16.50 

Carpenter  work  on  mast  and  boom  at  $2.50  a  -\ 
day    25.00 


QUARRYING   STONE. 

Complete  set  of  derrick  irons,  sheaves,  etc.  .$219.00 
2,400  ft.  best  galv.  i-in.  iron  rope  for  8  guys. 237.00 

Thimbles,  clamps,  etc 25.00 

500  ft.  steel  hoisting  rope,  I  y%  in 240.00 

Labor  on  dead  men,  4  men,  2  days  at  $1.40.  11.20 
Labor  raising  derrick,  8  men,  2  days,  at  $1.40  22.40 
Labor  fixing  guys,  8  men,  2  days,  at  $1.40.  22.40 

Total   $891.50 


197 


Fig.  25. 


Fig.  26. 

Knox  System  of  Blasting. — In  Trans.  Am.  Soc.  C.  E., 
1891,  Mr.  William  L.  Saunders  describes  the  Knox  system 
of  blasting,  named  after  the  inventor.  (The  patents  have 
recently  expired.)  The  system  consists  in  drilling  a  num- 
ber of  ordinary  round  holes  in  a  row  and  then  using  a  ream- 
ing tool  to  give  the  hole  the  shape  shown  by  the  heavy  lines 
in  Fig.  25.  The  reaming  is  done  by  hand.  In  medium  sand- 
stone the  holes  may  be  10  to  15  ft.  apart,  but  in  limestone 
I  find  that  they  are  often  placed  as  close  together  as  4  ft. 
The  holes  are  charged  with  black  powder,  or  with  Judson 


ig8        ROCK  EXCAVATION— METHODS  AND  COST. 

powder,  as  shown  in  Fig.  26,  a  wad  of  hay  being  put  in  so 
as  to  make  an  air  space  between  the  powder  and  the  tamp- 
ing. The  blast  causes  the  rock  to  split  in  a  straight  line  in 
the  direction  of  the  pointed  or  wedge-shaped  sides  of  the 
hole.  For  block-holing,  where  it  is  desired  to  split  a  block 
into  just  four  pieces,  a  single  hole  is  reamed  as  shown  in 
Fig.  27. 

Saunders  gives  the  following  data:  At  Portland,  Conn., 
15  Knox  holes  in  brown  sandstone,  charged  with  2  Ibs.  of 
black  powcjer  (No.  C)  in  each  hole,  loosened  a  block  of  rock 
1 10  ft.  long,  20  ft.  wide  and  1 1  ft.  thick,  weighing  2,400  tons. 


Line  of 


Fracture 


Fig.  27. 

This  block  was  split  off  and  moved  out  2  ins.  en  masse.  An- 
other sandstone  ledge,  open  face  and  ends,  was  blasted  with 
i  Ib.  of  powder  in  each  of  25  holes,  and  a  block  200  ft.  long, 
28  ft.  wide  and  15  ft.  deep  was  broken  off  and  moved  J^  in. 
At  the  mica  schist  quarries  at  Conshohoken,  Pa.,  a  blast  of 
y2  lb.  of  powder  in  a  single  hole  broke  a  block  27  ft.  long, 
15  ft.  wide  and  6  ft.  thick  across  the  rift. 

Cost  of  Quarrying  for  the  Buffalo  Breakwater. — In  Engin- 
eering News  May  16,  1901,  Mr.  Emile  Low  (in  an  article 
on  the  Buffalo  breakwater)  gives  data  on  quarrying  by  the 
Knox  system.  The  contractors,  Hughes  Bros.  &  Bangs, 
signed  their  contract  Jan.  27,  1897,  at  the  following  prices: 
Gravel  hearting,  13  cts.  per  cu.  yd. ;  rubble  stone,  80  cts.  per 


QUARRYING   STONE.  IQ9 

ton  of  2,000  Ibs. ;  capping  stone  and  revetment,  $1.25  per 
ton.  No  work  was  done  in  the  winter.  Water  telescopes 
were  used  in  placing  the  revetment.  Of  revetment,  235 
tons  were  placed  daily,  the  stone  weighing  6  2/3  tons  each 
on  an  average,  and  up  to  a  maximum  of  17  tons.  All  scows 
were  provided  with  glass  gages  and  graduated  rules  for 
weighing  the  stone.  A  gage  is  made  of  3-in.  wrought  iron 
standpipe,  into  which  two  brass  cocks  are  screwed.  Be- 
tween the  cocks,  which  are  4^  to  7  ft.  apart,  depending  on 
the  draft  of  the  scow,  is  placed  a  i-in.  glass  tul^e;  and  a 
wooden  rule  graduated  to  hundredths  of  a  foot  is  attached 
alongside.  Lockport  limestone  weighing  165  Ibs.  per  cu.  ft. 
solid,  and  Medina  sandstone  weighing  152  Ibs.  per  cu.  ft. 
solid  were  used  for  small  rubble.  T|br  voids  in  the  broken 
stone  were  50  per  cent. 

Most  of  the  stone  used  was  a  limestone,  quarried  near 
Windmill  Point,  Ontario,  and  weighed  166  Ibs.  per  cu.  ft. 
The  stone  was  taken  out  in  four  ledges ;  the  first,  20  to  36 
ins.  thick ;  the  second,  6  to  9  ft. ;  the  third,  7  to  10  ft. ;  the 
fourth,  5  ft.     In  opening  the  quarry  a  trench  30  ft.  deep  x 
100  ft.  wide  was  made  as  rapidly  as  possible,  using  heavy 
charges  of  dynamite.    In  quarrying  the  face  was  worked  in 
four  ledges.     The  top  ledge  was  drilled  with  holes  18  ft. 
back  from  the  face  and  4  ft.  apart,  the  holes  going  down  to 
within  6  ins.  of  the  bottom  of  the  ledge.     An  attempt  was 
made  to  start  and  end  at  a  joint,  so  the  ledge  could  be  moved 
entire  for  200  ft.  or  so.    Three  sizes  of  Ingersoll-Sergeant 
steam  drills  were  used:  A   (2^  in.)  ;  C   (2^  in.),  and  F 
(3^2  in.).   At  a  depth  of  18  ft.  the  hole  was  1^4  ins.  diam., 
losing  yi-'m.  every  3  ft.     After  the  holes  were  drilled  they 
were  reamed  to  an  elliptical  shape  (Knox  hole)  by  a  dia- 
mond-shaped tool  driven  either  by  hand  or  by  steam.    Black 
powder  was  charged,  3  or  4  handfuls  in  each  hole  first ;  then 
the  exploder,  then  a  little  more  powder ;  then  a  wad  of  grass 
was  forced  down  leaving  2  or  3  ins.  of  air  above  the  charge ; 
then  a  clay  tamping  to  the  top  of  the  hole.     Dry  sand  is 


200        ROCK  EXCAVATION— METHODS  AND  COST. 

sometimes  used  instead  of  clay,  being  more  quickly  placed, 
and  giving  good  results.  Sand  is  also  easier  to  clean  out  in 
case  of  misfire.  To  clean  out  a  misfire  hole,  a  steam  hose  is 
attached  to  small  pipe  through  which  steam  and  water  are 
blown  as  the  pipe  descends,  thus  blowing  out  the  charge. 

One  block  of  stone,  180  ft.  long,  18  ft.  wide  and  9  ft. 
thick,  weighing  2,430  tons,  was  blasted  off  by  one  firing, 
requiring  52  holes,  8  to  9  ft.  deep,  18  ft.  from  the  face  and 
$l/2  ft.  apart,  loaded  with  75  Ibs.  of  black  powder.  These 
52  holes  were  loaded  and  tamped  with  sand  in  I  hr.,  where 
it  would  have  taken  2^2  to  3  hrs.  with  clay.  The  block, 
(1,080  cu.  yds.)  was  moved  2  ft.  by  the  75  Ibs.  of  powder, 
that  is,  i  Ib.  of  powder  loosened  14  cu.  yds.  of  solid  rock. 

Another  (3,375-ton)  block  250  ft.  long,  9  ft.  thick  and 
18  ft.  wide,  was  thrown  out  (2  to  3  ft.)  with  150  Ibs.  of 
powder  in  62  holes 

After  these  large  blocks  were  separated  from  the  ledge, 
they  were  split  up  by  drilling  holes  and  using  either  plug  and 
feathers  or  light  powder  charges. 

The  plant  consisted  of :  2  A,  9  C  and  3  F  drills ;  8  derricks 
in  the  quarry  and  I  at  the  loading  dock;  4  5o-h.-p.  boilers 
for  derricks;  4  skeleton  2O-h.-p  (8^4  x  12-in.)  hoisting  en- 
gines for  8  quarry  derricks;  I  hoist  and  boiler  for  hauling 
cars  up  incline;  I  boiler  for  2  steam  pumps  for  draining 
quarry;  I  dinky  locomotive;  50  cars,  3-ft.  gauge;  68  skips, 
holding  3  to  4  tons,  for  carrying  stone  on  flat  cars;  black- 
smith shop  and  5  forges;  machine  shop;  track,  etc. 

The  force  during  June,  1903,  was  as  follows: 

Rates  of  Total  per 

General :  wages.  lo-hr.  day. 

I  superintendent   $167.00  per  mo.     $7.00 

I  time  keeper   60.00  per  mo.       2.25 

i  general  foreman 85.00  per  mo.      3.25 

Stripping  gang: 

i  foreman   2.25  2.25 


QUARRYING   STONE. 


201 


4  laborers $1.50  $6.00 

I  team  3.00  3.00 

Quarry : 

i  asst.  genl.  foreman 3.00  3.00 

8  foremen  (one  per  derrick) .  2.25  18.00 

14  machine  drillers 2.00  28.00 

14  machine  drillers  helpers.  ...  1.50  21.00 

4  hoist  engineers   (derricks) .  1.75  7.00 
i  hoist     engineer       (inclined 

plane)    1.75  1.75 

5  firemen    1.75  8.75 

50  laborers    1.50  75-°o 

i  water  boy i.oo  i.oo 

i  watchman 1.75  1.75 

i  team  3.00  3.00 

Loading  dock : 

i  foreman    2:25  2.25 

i  hoist  engineer   1.75  1.75 

i  fireman    1.75  1.75 

6  laborers   1.50  9.00 

i  watchman    1.75  1.75 

Track  repairs : 

i   foreman    2.25  2.25 

3  laborers    1.50  4.50 

Blacksmith  shop : 

i   foreman    3.00  3.00 

3  blacksmiths   2.50  7.50 

3  helpers   1.75  5.25 

Others : 

i  locomotive  driver  2.50  2.50 

1  machinist   75-OO  per  mo.       3.00 

2  carpenters    1.75  3.50 


Total,         $240.00 


202        ROCK  EXCAVATION— METHODS  AND  COST. 


TABLE  XXI. 


Month, 
1903. 
May    .... 
June   .... 
July    .... 
Aug  
Sept  
Total    .  .  . 

Stone  quar: 
Rubble. 

16,535-9 
12,771.2 
11,444.4 
9,426.2 
5,937-0 
56,114.7 

ried,  tons  oi 
Capping. 

:  2,000  Ibs. 
Total. 

16,535-9 
15,312.6 
16,718.2 
14,544-9 
8,868.9 
71,980.5 

2,541-4 
5,273-8 
5,n8.7 
2,931-9 
15,865.8 

TABLE  XXII. 


Cost  of      Cost  per 
Labor  only.  Ton,  cts. 
$5,127.51 
5,154.65 
5,438.91 
5,071.92 

3,283.85 


24,076.84 


31 
34 
33 
35 
37 
33 


Explosives,  Ibs. 


Month, 
1903. 

May    
July    ...... 
AUg  

No.    Holes    per 
Day  per  Drill. 
A          C        F 
12.5      10.0      8.8 
13-8        9-5      9-5 
13.3        94      9-4 

Average    Depth 

of  Holes. 
A        C        F 


2.7 
1-7 


5-3 
5-i 


8.7 

7-3 


Month,           Days     No.  of  holes  drilled.  Lin.  ft.  drilled.               |  £     g  c 

1903.         Worked.  A        C        F  Total.      A           C         F       Total.     £  Q     US 

May       2^/2    513      896   556   1,965    1,385  4,757  4,840   10,982   1,691  302  211 

July       .....    2^/2   674  2,101   674  3,449   1,177  10,771   4,927   16,875   2,683  292  226 

Aug 23.7  620   1,978  658  3,256      853  10,098  4,677   15,628  2,558  117  236 

TABLE  XXIII. 

Lin.  Ft.  of  Hole 
per  Day  per 

Drill. 

A          C          F 
33.8      53.4      76.2 
24.0      49.0      67.0 
18.4      47.3      65.8      1.3      5.1      7.1 
About  i  Ib.  of  black  powder  was  used  for  every  7  tons 
of  stone  quarried,  and  I  Ib.  of  dynamite  for  every  67  tons, 
and  i  ft.  fuse  for  every  $y2  tons  of  stone. 

The  cost  of  powder,  dynamite  and  fuses  per  ton  of  stone 
was:   In  May,  i.  3  cts.;  July,  2.0  cts. ;  August,  2.1  cts. 

The  total  cost  of  quarrying  stone,  loading  and  placing  on 
seows  was  as  follows : 

Cost  per 
ton,  cts. 

Labor    33 

Coal    4 

Explosives    2 

Miscellaneous   5 


Cost  per 
cu.  yd.,  cts. 

74-3 
9.0 

4-5 
1 1.2 


Total    44  99.0 

Cost  of  Quarrying  Dimension  Sandstone. — In  Engineering 
News,  Nov.  2i,  1901,  Mr.  R.  C.  McCalla,  Jr.,  gives  the  foJ- 


QUARRYING   STONE.  203 

lowing:  In  October,  1891,  200  cu.  yds.  of  backing  and  600 
cu.  yds.  of  dimension  stone  were  quarried  for  Lock  2,  Black 
Warrior  River,  Tuskaloosa,  Ala.  The  stone  was  a  fine  qual- 
ity of  blue  sandstone  quarried  from  the  bed  of  the  river  at 
the  falls,  after  diverting  the  water.  The  cost  of  qarrying 
these  800  cu.  yds.  was  $1,598,  or  about  $i  per  cu.  yd.  for 
the  backing  and  $2.33  per  cu.  yd.  for  the  dimension  stone. 
In  this  month  434  cu.  yds.  of  dimension  stone  were  cut  by 
stone  cutters  at  a  cost  of  $6.83  per  cu.  yd.  The  masonry  wall 
is  390^  ft.  long,  8  to  14  ft.  wide,  and  34  ft.  high,  built  in 
courses  of  ashlar  18  to  24  ins.  thick,  and  about  50  per  cent, 
cut  stone.  In  October  two  gangs  of  masons,  using  two  der- 
ricks, laid  1,563  cu.  yds.  of  first-class  masonry  at  a  total  cost 
of  92^  cts  per  cu.  yd.,  including  the  cost  of  screening  sand, 
mixing  mortar,  operating  steam  hoists,  unloading  material 
at  the  wall  and  converting  them  into  masonry.  The  itemized 
cost  of  the  mason  work  was : 

Foreman,  I  mo $90.00 

Masons,     202       days  of  8  hrs.,  at  $2.80    .  . .     565.60 

Laborers,    35^  "     $1.20    ...       42.15 

270^  "     $1.00    ...     270.50 

369^  "         "         "     $  -80    ...     295.70 

14634  "     $  .60    ...       88.05 

Boys,       ,    83^  "     $  .40    ...       33.30 

Wages  paid  in  board 42.00 

Fuel  for  hoists 18.49 


Total,  at  925^  cts.  per  cu.  yd $1,445.79 

Quarrying  by  Water  Cushion  Blasts. — The  following 
method  of  quarrying  is  described  in  Engineering  Record, 
April  7,  1900: 

At  Cobleskill,  N.  Y.,  limestone  was  quarried  for  the  back- 
ing of  the  East  River  Bridge  piers.  Most  of  the  backing  is 
laid  in  3-ft.  courses ;  the  stone  is  remarkable  for  its 
smoothness,  many  beds  requiring  no  dressing.  The  quarry 
is  a  solid  stratum  28  ft.  thick,  with  vertical  fissures  at  right 


204        ROCK  EXCAVATION— METHODS  AND  COST. 

angles  to  each  other  and  up  to  100  ft.  apart.  A  row 
of  vertical  holes  3  or  4  ft.  apart  is  drilled  through  the 
stratum  from  3  to  10  ft.  back  of  the  face,  depending  on  size 
of  blocks  required.  The  holes  are  filled  three-quarters  full 
with  water,  plugged,  and  a  charge  of  black  powder  put  in 
over  the  plugs  and  tamped.  When  fired,  a  block  of  solid 
rock  28  ft.  high  and  perhaps  100  ft.  long  and  6  ft.  thick,  was 
separated  and  remained  standing  in  its  original  position. 
Cross  rows  of  vertical  holes  were  drilled  and  fired  similarly 
to  the  first  holes,  breaking  the  stone  into  blocks  10  ft.  long 
and  28  ft.  high.  These  blocks  were  thrown  over  and  split 
with  plug  and  feathers  into  blocks  of  thickness  required 
for  the  courses. 

Granite  Quarrying. — In  most  granite  quarries  steam  drills, 
derricks  and  hoisting  engines  are  the  only  machines  used. 
In  "sheet  quarries"  after  a  trench  is  blasted  out  to  open  up 
a  face,  if  no  natural  face  exists,  then  the  two  ends  of  the  face 
are  freed  by  making  channels. 

At  the  Crotch  Island  quarries,  in  Maine,  two  parallel 
rows  of  holes  are  drilled  3  ft.  apart,  the  holes  in  each  row 
being  8  ins.  apart  and  as  deep  as  the  sheet  of  granite,  which 
varies  from  2  to  16  ft.  thick.  These  holes  are  charged  with 
60  per  cent,  dynamite,  two  sticks  at  the  bottom  of  each  hole, 
then  a  plug  of  wood  8  ins.  long  on  top,  then  a  stick  of  dyna- 
mite 8  ins.  long  on  top  of  the  wood,  then  another  plug  of 
wood,  and  so  on  until  within  I  ft.  of  the  mouth  of  the  hole, 
which  is  tamped.  A  cap  is  placed  in  the  last  cartridge  in 
each  hole,  and  the  holes  are  fired  in  pairs.  It  is  not  neces- 
sary to  put  a  cap  in  any  of  the  lower  sticks  as  the  shock 
sends  them  all  off  practically  together.  This  heavy  loading 
results  in  tearing  the  granite  into  chips  which  are  often 
hurled  a  great  distance,  necessitating  blasting  at  night ;  but 
the  powdered  granite  left  in  the  channel,  is  easily  shoveled 
out,  leaving  a  trench  about  4^  ft.  wide.  Having  freed  the 
two  ends,  a  long  block  of  granite,  the  thickness  of  the  sheet, 
is  loosened  by  blasting.  The  granite  adjoining  the  channels 


QUARRYING   STONE.  205 

when  cut  into  blocks  shows  no  sign  of  weakness  in  spite  of 
the  tremendous  blow  received  in  blasting. 

I  am  indebted  to  the  Engineering  Record  for  the  follow- 
ing description  of  the  Crotch  Island  quarry : 

A  diagram  of  the  method  of  working  is  shown  in  Fig. 
28,  not  made  to  scale  or  true  dimensions,  but  merely  indi- 
cating the  operations.  1-2-3-4  and  5  are  successive  strata 
of  increasing  height  and  from  5  to  12  ft.  thick.  Suppose 
that  strata  4  is  9  ft.  thick  and  it  is  desired  to  quarry  from 
it  stones  12  ft.  long.  On  the  required  line  B-H  a  pair  of 
L.ewis*  holes  about  12  ins.  apart  and  9  ft.  deep  are  made  at 


Vertical  Quarrvffr 


IK     K     K     K 


Channel          Vertical  Quarry  Face* 

3 
Vertical  Quarry  Face* 


Vertical  Quarry  Face* 


D  with  a  compressed  air  drill  and  black  powder  is  fired  in 
them;  they  are  swabbed  out,  recharged  and  retired,  and  so 
on  several  times  until  a  crack  has  been  opened  from  J  to  L. 
Another  similar  pair  of  Lewis  holes  is  made  in  the  line  of  the 
crack  about  40  ft.  away  at  E  and  they  are  similarly  fired. 
Holes  are  drilled  at  G-H  and  so  on,  and  the  crack  is  pro- 
duced as  far  as  desired,  extending  everywhere  through  to 
the  stratum  below.  Holes  9  ft.  deep  are  drilled  8  to  12  ins. 


Any  drill  holes  placed  close  together  are  called  Lewis  holes. 


206        ROCK  EXCAVATION— METHODS  AND  COST. 


apart  in  two  rows  3  ft.  apart  from  A  to  B,  adjacent  to  the 
open  seam  which  bounds  one  side  of  the  quarry  to  form  the 
channel.  The  pair  of  holes  nearest  A  are  heavily  loaded 
with  dynamite  and  fired  as  above  described,  then  the  next 
pair  are  fixed,  and  so  on.  Each  blast  pulverizes  the  granite 
between  and  close  to  the  holes  and  throws  the  fragments  so 
.far  that  these  blasts  are  fired  at  night  when  only  the  two 
men  in  charge  remain  on  the  island.  When  the  whole  set  of 
holes  has  been  fired  a  channel  has  been  formed  about  3^2  ft. 
wide  which  extends  through  the  stratum  from  A  to  B  and 
gives  a  free  face.  The  slab  A-B-H-M,  12  ft.  wide,  9  ft. 
thick,  and  perhaps  300  ft.  long,  is  thus  detached  from  the 
stratum,  but  is  not  moved  more  than  the  fraction  of  an  inch 
from  its  original  position.  Blocks  of  any  required  width 
are  laid  off  by  lines  (K-K-K,  etc.)  of  small  holes,  which  are 
drilled  by  hand,  and  the  stone  is  split  along  them  by  the 
regular  plug  and  feather  method. 


..Main  Hoist 


Overhauling 
Weight-'' 


^-Single  Hoist  Line 

Extension  of  Line 


Quarry  Floor*. 


~fc  Hoisting 

"-'—' 


Fig.  29. 


The  method  of  removing  these  blocks  is  ingenious.  Dog 
holes  are  made  in  each  and  the  main  line  from  a  derrick, 
Fig.  29,  is  attached  and  a  strain  is  put  on  by  the  engine,  but 
does  not  move  it.  The  crack  B-H  is  perhaps  1/8  to  1/16  in. 
wide,  and  in  it,  opposite  the  center  of  the.  blocks,  are  poured 
two  cups  of  .thick  black  oil  at  points  about  a  foot  apart. 


QUARRYING   STONE.  207 

Between  these  points  is  poured  a  handful  of  black  powder, 
which  is  covered  with  dirt,  and  has  a  fuse  attached.  The 
powder  does  not  spread  beyond  the  oil  line,  and  so  is  con- 
fined in  a  thin  sheet,  filling  the  crack  from  top  to  bottom. 
When  the  fuse  is  lighted  there  is  a  light  explosion  which 
does  not  break  the  stone,  but  suffices  to  kick  it  out  of  its 
place  and  thus  started,  is  easily  pulled  by  the  derrick  line, 
over  the  smooth,  steep  slope  of  the  underlying  stratum  to 
a  point  within  reach  of  the  derrick  boom.  There  it  is  split 
into  required  sizes  by  plug  and  feathers,  and  the  pieces  are 
loaded  by  the  derrick  on  cars,  lowered  down  inclined  track 
by  cables  to  the  two  docks  where  other  derricks  load  them 
on  schooners  for  shipment. 

Quarrying  Massive  Granite. — When  granite  does  not  occur 
in  beds  or  sheets  of  moderate  thickness,  the  method  just  de- 
scribed requires  some  modification.  The  method  practiced 
at  Mt.  Airy,  in  North  Carolina,  according  to  Merrill,  is  as 
follows:  No  quarry  face  is  used,  but  a  hole  is  drilled  in 
the  massive  granite  perpendicular  to  the  surface,  and  to  a 
depth  of  6  to  12  ft.,  according  to  the  thickness  of  the  stone 
desired.  This  hole  is  loaded  with  a  light  charge  of  powder 
and  fired,  then  it  is  loaded  with  another  light  charge  and 
fired,  and  so  on  until  cracks  appear  in  the  granite  at  the  sur- 
face at  a  distance  of  150  to  200  ft.  from  the  hole,  caused  by 
the  lifting  bodily  of  a  lense-shaped  mass  of  the  granite  by 
the  force  of  the  powder.  The  blasting  is  repeated  until  the 
lense-shaped  mass  is  almost  free  all  around,  when  it  is  left 
for  a  day  or  two  so  that  the  stresses  produced  by  the  changes 
of  temperature  from  day  to  night  break  the  mass  of  granite 
entirely  free.  Then  this  lenticular  mass  is  split  with  wedges 
into  blocks  that  can  be  removed.  This  is  a  very  ingenious 
method  and  one  well  worthy  of  introduction  wherever  gran- 
ite occurs  in  massive  form,  but  the  most  common  method  is 
as  follows: 

The  granite  is  blasted  out  in  large,  irregular  chunks,  using 
as  small  charges  of  powder  as  will  effect  the  loosening  of 


208        ROCK  EXCAVATION— METHODS  AND  COST. 

the  rock,  the  method  being  in  fact  similar  to  ordinary  open 
cut  excavation  described  in  Chapter  XII.  The  largest  and 
most  regular  blocks  are  selected  for  splitting  up  with  plug 
and  feathers,  and  the  other  stones  are  used  as  far  as  possible 
for  rubble  or  concrete.  In  upper  New  York,  on  the  Spier 
Falls  Dam  construction,  and  in  Massachusetts,  on  the  Wa- 
chusett  Dam  work,  I  have  seen  this  method  used  on  a  large 
scale.  On  a  smaller  scale  I  have  used  it  myself,  but  in  all 
cases  the  cost  of  the  dimension  stone  so  secured  has  been 
excessive.  The  Adirondacks  "granite"  is  an  exceedingly 
tough  stone,  but  in  spite  of  the  greatest  care  I  have  had  cut 
stone  break  in  two  while  handling  them,  because  of  the 
shattering  effect  of  the  dynamite ;  and  black  powder  did  not 
prove  much  more  satisfactory.  On  both  the  large  dams  just 
mentioned  it  was  found  cheaper  to  import  cut  stone  long 
distances  than  to  use  the  local  granite  for  certain  parts  of 
the  cut  stone  work.  If  granite  boulders  occur,  they  can  be 
split  up  with  plug  and  feathers  yielding  splendid  blocks.  In 
fact  the  early  qarrying  in  a  granite  region  is  apt  to  be 
boulder  quarrying ;  and,  in  consequence,  quarries  of  massive 
granite  that  is  blasted  out  in  rough  chunks  and  split  with 
plugs  and  feathers,  are  often  called  boulder  quarries. 

An  effective  way  of  making  "boulders"  is  by  large  cham- 
ber blasting,  where  the  amount  of  stone  required  warrants 
quarrying  on  such  a  large  scale. 

Cost  of  Quarrying  Granite. — Cost  data  relating  to  the 
quarrying  of  granite  dimension  stone  are  extremely  hard  to 
secure.  I  have  been  able  to  find  only  one  writer,  Mr.  J.  J.  R. 
Croes,  who  has  published  anything  on  the  subject.  Mr. 
Croes'  records,  together  with  mine,  will  at  least  form  a  basis 
for  approximate  estimates  of  cost  of  granite  quarrying.  My 
data  apply  to  quarrying  three-dimension  stone  in  a  sheet 
quarry  on  the  coast  of  Maine.  The  total  number  of  men  en- 
gaged was,  on  the  average:  6  enginemen,  6  steam  drillers,  6 
drill  helpers,  3  blacksmiths,  3  helpers,  5  tool  and  water  boys, 
38  quarrymen,  47  laborers,  2  foremen  and  I  superintendent. 


QUARRYING   STONE.  209 

This  force  quarried  and  loaded  on  boats  about  1,400  cu.  yds. 
of  rough  granite  blocks.  The  stone  was  loaded  by  derricks 
onto  cars,  from  which  it  was  unloaded  into  boats  ready  for 
shipment.  The  following  cost  includes  everything  except 
interest  and  depreciation  of  plant,  and  development  ex- 
penses : 

Cost,  per  cu.  yd. 

Enginemen,  at  $2  a  day  (of  9  hrs.) $0.20 

Steam  drillers,  at  $2.00 0.20 

Drill  helpers,  at  $1.50   0.15 

Blacksmiths,  at  $2.75   0.14 

"  helpers,  at  $1.75    0.09 

Tool  and  water  boys,  at  $i    0.16 

Quarrymen,  at  $1.75 1.09 

Laborers,  at  $1.50 1.15 

Foremen,  at  $3 15 

Superintendent,  at  $8 20 

Coal,  at  $5  ton   45 

Explosives 25 

Other  supplies 30 


Total .  $4-53 

On  the  best  month's  work,  when  a  larger  force  was  being 
operated,  the  cost  of  all  labor,  superintendence  and  supplies, 
was  reduced  to  a  little  below  $4  per  cu.  yd. ;  but  the  above, 
$4.50  per  cu.  yd.,  may  be  taken  as  a  fair  average  of  several 
months'  work.  To  this  should  be  added  the  charges  for 
plant  rental,  quarry  rental  (if  any),  stripping  (if  any),  and 
freight  charges  to  destination.  The  freight  rate  by  boat 
from  Maine  to  New  York  is  about  $i  a  ton,  but  as  rough 
granite  blocks  are  always  measured  on  their  least  dimen- 
sions, the  freight  charges  when  $i  per  ton  amount  to  about 
$2.70  per  cu.  yd.,  of  three-dimension  stone  in  the  rough. 
The  explosives  used  were  black  powder,  costing  $2.25  a  keg 
(25  Ibs.),  and  dynamite  for  channeling,  costing  15  cts.  a  Ib. 
The  sheet  from  which  this  granite  was  quarried  averaged 


210        ROCK  EXCAVATION— METHODS  AND  COST. 

about  6y2  ft.  thick,  and  was  nearly  flat.  The  stone  was 
loosened  in  long  blocks  by  Knox  blasting  with  black  powder, 
and  was  split  up  into  sizes  by  plug  and  feathering;  both 
hand  drills  and  pneumatic  plug  drills  being  used  for  this 
purpose.  The  stone,  as  before  stated,  was  three-dimension 
stone.  To  quarry  random  stone  (not  rubble)  in  this  quarry 
cost  about  $3.50  per  cu.  yd. 

Cost  of  Quarrying  Gneiss. — Brief,  but  reliable  data  on  the 
quarrying  of  stone  for  the  Boyd's  Corner  Dam,  near  New 
York  City,  are  given  by  Mr.  J.  J.  R.  Croes,  in  Trans.  Am. 
Soc.,  C.  E.,  1875.  The  stone  is  a  gneiss  that  is  found  in  and 
about  New  York  City,  and  containing  so  much  mica 
that  it  is  more  properly  called  mica-schist.  The  face  stone 
for  the  dam  average  1.8  ft.  rise,  3.6  ft.  long  and  2.7  ft.  deep, 
and  were  cut  to  lay  24-in.  joints.  In  quarrying  the  dimension 
stone,  plug  and  feathers  were  used  to  split  the  stone  to  size 
ready  for  cutting.  The  cost  of  quarrying  and  plug  and 
feathering  4,000  cu.  yds.  of  dimension  stone  ready  for  cut- 
ting was  as  follows : 

Days   ( 10-hr.)     Cost  per 
per  cu.  yd.         cu.  yd. 

Foreman,  at  $3  0.114  $0.34 

Drillers,  at  $2   0.917  1.84 

Laborers,  at  $1.50 0.429  0.65 

Blacksmiths,  at  $2.50 0.102  0.25 

Tool  boys,  at  $0.50 0.108  0.05 

Labor  loading  teams,  at  $1.50. . .  0.284  0.42 


Total    (not    including    explo- 
sives  and   teaming)    $3-55 

The  work  was  done  by  contract  in  1867-8.  The  rates  of 
wages  were  not  given  by  Mr.  Croes,  but  Mr.  John  B.  Mc- 
Donald has  been  kind  enough  to  give  me  most  of  the  rates  of 
wages  as  nearly  as  he  can  remember.  The  length  of  haul 
from  quarry  to  stone  yard  was  about  a  mile,  and  Mr.  Mc- 
Donald states  that  oxen  were  used.  The  cost  of  "teams"  is 


QUARRYING   STONE.  211 

given  by  Mr.  Croes  as  0.62  team  days  per  cu.  yd.,  which  indi- 
cates that  a  good  deal  of  stone  boat  work  was  done,  or  else 
that  there  is  an  error  in  this  item. 

The  cost  of  quarrying  3,400  cu.  yds.  of  rubble  stone  for 
this  same  dam  was  as  follows : 

Days  per       Cost  per 
cu.  yd.  cu.  yd. 

Foremen,  at  $3    0.041  $0.12 

Drillers,   at  $2    0.339  °-68 

Laborers,  at  $1.50 0.140  0.21 

Blacksmiths,  at  $2.50    0.036  0.09 

Tool  boy,  at  $0.50  0.035  0.02 

Labor,  loading  teams,  at  $1.50. .  0.077  0.12 

Teams,  at  $4 0.141  0.56 


Total  labor  $1.80 

It  is  presumable  that  both  the  dimension  stone  and  the 
rubble  stone  were  measured  in  the  dam. 

Cost  of  Quarrying  Sandstone. — In  quarrying  thin  bedded 
sandstone  for  dry  slope  walls  and  rubble,  I  have  found  that 
one  quarryman  will  average  about  2  cu.  yds.,  per  lo-hr.  day. 
In  doing  this  work  no  powder  is  used  where  the  beds  lie  free, 
but  if  they  are  cemented  together  it  is  necessary  to  shake 
up  the  ledge  with  light  charges  of  black  powder.  Wedges, 
crow-bars  and  hammers  are  the  only  tools  needed  for 
quarrying  thin  bedded  stone  where  the  beds  can  be  separated 
by  driving  wedges  in  between  them.  The  stone  quar- 
ried thus  is  not  very  regular,  except  on  the  bed  joints ;  and, 
when  it  is  dressed  up  by  the  mason,  there  is  a  considerable 
shrinkage  in  volume  between  the  measurement  of  the  stone 
corded  on  a  stone  rack  and  the  stone  measured  in  the  wall. 
The  mason  uses  the  spalls  to  fill  in  the  vertical  joints,  so  that 
there  is  little  or  no  real  loss  of  stone.  In  quarrying  several 
thousand  cu.  yds.  of  stone  for  dry  slope  wall  masonry,  I 
found  that  2  cu.  yds.  of  stone,  measured  corded  on  the 
wagon,  made  1.55  cu.  yds.  of  slope  wall.  Each  quarryman 


212        ROCK  EXCAVATION— METHODS  AND  COST. 

averaged  2  cu.  yds.  per  day  of  stone  as  measured  in  the  wall, 
or  2.6  cu.  yds.,  measured  corded  in  wagons.  These  quarry- 
men  received  $1.75  a  day,  and  as  practically  no  powder  was 
used,  the  cost  was  88  cts.  per  cu.  yd.  for  quarrying  stone 
measured  in  the  wall,  and  this  included  loading  onto  wagons, 
but  not  hauling. 

Cost  of  Quarrying  Limestone. — Mr.  James  W.  Beardsley  is 
my  authority  for  the  following  data  on  the  cost  of  quarrying 
limestone  for  retaining  walls  on  the  Chicago  Canal.  The 
contractors  selected  parts  of  the  canal  where  the  limestone 
occurred  in  strata  that  were  uniform,  so  that  the  beds  of 
the  stone  quarried  required  no  dressing.  The  stone  was  laid 
in  courses  averaging  about  15  ins.  thick,  the  better  stone  be- 
ing selected  for  the  face  of  the  wall.  Guy  derricks  having  a 
capacity  of  6  to  10  tons,  boom  40  to  60  ft.  long,  operated  by 
a  hoisting  engine,  were  used  for  loading  the  stone.  Black 
powder  was  used  to  shake  up  the- ledges,  and  the  stone  was 
then  barred  and  wedged  out.  The  cost  per  cu.  yd.  is  the 
average  of  93,500  cu.  yds.,  measured  in  retaining  walls. 
The  mortar  was  only  13%  per  cent,  of  the  wall;  indicating  an 
unusually  even  bedded  stone  that  squared  up  well.  The  cost 
does  not  include  general  superintendence,  installation  of 
plant,  plant  rental,  powder,  material  for  repairs,  and  cost 
arising  from  delays. 

•4-1 

Scrt       C  <D      "*^  3      £ 

<U          <U      QJ  (_)      ,-?  O      O 

'a  £       bj°  ^  8       *->      r 

£»  °      ;>    £    £       v  o  -a 

Hfo     ;>   a  ,c     Pn  "o      U   x 

General  foreman  ....  o.oi  $4.75  00.2  00.2 

Foreman i.oo  3.50  10.6  '     7.8 

Derrickmen    2.11  1.50  10.1  7.5 

Quarrymen 8.42  1.65  42.2  31.2 

Enginemen i.io  2.25  7.0  5.2 

Firemen    0.04  1.75  0.2  0.2 

Laborers 2.28  1.50  10.9  8.0 

Water  boys   0.33  0.75  0.9  0.7 


QUARRYING   STONE.  213 

Blacksmiths  0.27        2  to  3       1.7         1.3 

helpers  .  .   0.18         1.75         0.9         0.7 

Carpenters    0.02         2.25        o.i         o.o 

Drill   runners 0.36         2.00         3.1         2.3 

helpers 0.07         1.50        0.4        0.2 

Watchmen    0.04         1.50        o.i         o.i 

Teams  and  carts 0.29  3.50  and  2.50  3.8        2.8 

Derricks    -1.12         1.35         5.4         4.0 

Drills 0.36         1.15         2.1         1.5 

Total    16.52  (men)       99.7       73.7 

This  cost  of  73.7  cts.  per  cu.  yd.,  it  should  be  borne  in 
mind,  is  the  cost  of  quarrying  rubble  stone  occurring  in  regu- 
lar beds.  The  cost  of  quarrying  Manhattan  gneiss  and 
sledging  into  sizes  fit  for  rubble  is  given  on  page  222. 


CHAPTER  XII. 
OPEN  CUT  EXCAVATION. 

General  Considerations. — In  this  chapter  will  be  discussed 
all  open  cut  rock  work  except  trenching,  and  building  stone 
quarrying. 

The  removal  of  the  earth  "over  burden,"  as  the  English 
call  it,  or  the  "stripping"  is  it  is  termed  in  America,  is  dis- 
cussed in  my  book  on  earthwork,  so  that  no  space  will  be 
given  here  to  that  factor  of  cost.  In  selecting  a  quarry  site, 
of  course,  the  character  and  depth  of  stripping  should  al- 
ways receive  careful  consideration,  bore  holes  and  test  pits 
being  sunk  to  ledge  rock.  Another  feature  that  should  never 
be  overlooked  is  the  drainage.  A  pit  dug  below  the  level  of 
the  lowest  natural  drainage  channel  will  often  make  excava- 
tion exceedingly  expensive  where  much  water  flows  or  seeps 
into  it,  and  in  winter  it  may  drift  full  of  snow,  making  work 
impracticable.  I  have  opened  several  small  quarries  in  the 
bed  of  streams  that  run  nearly  dry  in  summer,  for  in  such 
places  the  stripping  is  likely  to  be  slight.  Quarries  are  pre- 
ferably located  in  the  side  of  a  hill  where  gravity  drainage 
will  be  secured.  Moreover,  in  such  a  location  there  is  gen- 
erally no  need  of  snatch  teams  or  hoisting  engines  to  haul 
the  wagons  or  cars  out  of  the  pit ;  whereas,  in  a  pit  below  the 
level  of  the  surrounding  country  there  is  a  constant  outlay 
of  money  for  raising  the  excavated  rock. 

Excavation  in  Benches. — In  deep,  open  cuts  or  pits,  the 
rock  is  usually  excavated  in  two  or  more  benches  or  lifts. 
On  the  Chicago  Canal,  for  example,  the  rock  cut  was  about 
36  ft.  deep,  and  it  was  taken  out  in  three  12-ft.  lifts.  There 
are  two  factors  that  determine  the  economic  height  of  a  lift: 
(i)  The  depth  to  which  the  drill  will  bore  economically, 
and  (2)  the  size  into  which  the  rock  breaks  upon  blasting. 

214 


OPEN  CUT  EXCAVATION.  215 

With  the  ordinary  3^-inch  drill,  about  16  to  20  ft.  is  the  lim- 
iting depth  of  economic  drilling,  but  with  a  3^2-in.  drill  it  is 
often  economic  to  drill  24  ft.  If  a  well  drilling  machine  is 
used,  it  is  possible  to  go  down  100  ft.  or  more,  and  in  fact,  I 
have  seen  a  shale  bench  60  ft.  high  taken  out  where  a  well 
driller  was  in  use.  The  height  of  the  bench,  however,  is  not 
dependent  solely  upon  the  economic  depth  of  drilling.  The 
higher  the  bench  the  farther  back  from  the  face  may  the 
row  of  drill  holes  be  located;  but  the  farther  back  that  the 
drill  holes  are  placed,  the  larger  will  be  the  chunks  of  rock 
thrown  down  upon  blasting,  unless  the  rock  is  exceedingly 
friable  like  shale.  If,  in  a  hard  limestone,  for  example,  the 
bench  is  25  ft.  high,  and  the  drill  holes  are  placed  in  a 
row  only  9  ft.  back  of  the  face,  the  blast  may  blow  out  the 
bottom  of  the  bench,  and  leave  the  top  overhanging;  and 
even  if  the  top  were  to  fall  it  would  come  down  in  very 
large  chunks,  although  the  bottom  might  be  broken  up  to 
the  desired  size.  This  objection  to  a  high  bench  with  drill 
holes  close  to  the  face  may  be  overcome  by  separating  the 
charge  in  each  hole  into  two  or  more  parts,  with  tamping 
between ;  and,  as  a  matter  of  fact,  I  am  surprised  that  this 
is  not  done  oftener. 

We  have  seen  in  Chapter  V.  that  it  pays  to  drill  as  deep  a 
hole  as  the  capacity  of  the  drill  will  permit  in  order  to  reduce 
the  time  lost  in  moving  from  hole  to  hole.  It  should  be 
added  that  the  depth  of  the  hole  should  ordinarily  be  some 
multiple  of  2  ft.  (if  the  feed  screw  is  2  ft.  long),  for  once 
a  new  bit  is  in  place  it  should  be  made  to  drill  as  far  as  the 
feed  will  permit.  This  rule  should  be  ignored  where  other 
reasons  prevail ;  thus,  in  stratified  rock  it  is  often  well  to 
stop  the  drill  hole  just  short  of  a  seam  of  stratification. 

In  order  to  increase  the  height  of  the  benches,  a  common 
expedient  is  to  drill  one  or  two  rows  of  horizontal  holes  in 
the  face  of  the  bench,  as  well  as  the  row  of  vertical  holes, 
as  shown  in  Fig.  32.  This  can  ordinarily  be  done  only  where 
the  bench  is  long  enough  to  permit  drillers  to  work  on  the 


2i6        ROCK  EXCAVATION— METHODS  AND  COST. 

floor  at  one  place  while  the  loaders  are  working  at  another 
place.  This  is  a  good  expedient  to  employ  where  one  port- 
able drilling  plant  is  used  to  work  two  or  more  quarries,  for 
in  this  way  a  high  bench  can  be  blown  down  at  one  blast, 
instead  of  taking  it  down  in  two  shallow  benches,  and  thus 
time  is  saved  in  moving  the  drilling  plant.  It  is  also  an  ex- 
pedient often  used  in  side  hill  cutting  where  a  steam  shovel 
is  used  for  loading. 

Spacing  Holes. — A  common  rule  is  to  place  the  row  of 
vertical  drill  holes  a  distance  back  from  the  face  equal  to 
the  depth  of  the  drill  hole,  and  to  place  the  drill  holes  a 
distance  apart  in  the  row  equal  to  their  depth.  Another 
rule  is  to  place  the  row  of  holes  back  from  the  face  a  dis- 
tance equal  to  three-fourths  their  depth,  and  the  same  dis- 
tance apart  in  the  row.  In  stratified  rock  of  medium  hard- 
ness these  rules  may  be  followed  in  making  the  first  experi- 
ments, but  they  will  lead  to  serious  error  if  applied  to  dense 
granitic  rocks.  In  the  limestone  on  the  Chicago  Canal,  not 


much   of   which 

steam      shovels, 

usually     12     ft. 

in  rows  about  8 

face    and    8   ft. 

holes     were 

per   cent,    dyna- 

way  cut  through 

holes   were   20   ft.   deep,    18   ft.   back 

14  ft.  apart  in  the  row.    These  holes  were 


Fig.  30. 


was  loaded  with 
the  holes  were 
deep  and  placed 
ft.  back  of  the 
apart.  These 
charged  with  40 
mite.  In  a  rail- 
sandstone  the 
from  the  face  and 
sprung"  three 


times,  and  each  hole  charged  with  200  Ibs.  of  black  powder. 
In  granite  quarried  for  rubble  for  dam  work,  I  have  had 
to  place  the  holes  4^2'  to  5  ft.  back  of  the  face  and  the  same 
distance  apart,  the  holes  being  12  ft.  deep,  about  2  Ibs.  of 
60  per  cent,  dynamite  being  charged  in  each  hole.  On  rail- 
way work  in  the  Rocky  Mountains  about  the  same  spacing 
was  found  necessary  in  granitic  rock  that  was  to  be  broken 
up  into  chunks  that  a  steam  shovel  could  handle.  In  pit 


OPEN  CUT  EXCAVATION.  217 

mining  at  the  Treadwell  Mine,  Alaska,  the  holes  are  drilled 
12  ft.  deep,  in  rows  2^  ft.  apart,  the  holes  being  6  ft.  apart 
in  each  row  and  staggered,  as  shown  in  Fig.  30.  This  re- 
quires drilling  1.7  ft.  of  hole  per  cu.  yd.  I  am  indebted  to 
Mr.  Robt.  A.  Kinzie  for  this  information.  The  ore  is  a 
tough  syenite,  and  the  holes  are  spaced  closer  together  than 
would  be  necessary  if  the  crushers  were  large  enough  to  re- 
ceive bigger  chunks.  In  crushing  ore  or  rock  on  a  large 
scale  the  mining  man  and  the  contractor  should  bear  in  mind 
that  it  is  poor  economy  to  install  small  crushers,  especially 
where  the  rock  is  so  tough  that  it  breaks  out  in  large  chunks ; 
for  a  small  crusher  means  not  only  money  lost  due  to  drill- 
ing holes  close  together,  but  it  usually  means  labor  and 
powder  expended  in  sledging  and  blockholing  the  rock  be- 
fore it  will  enter  the  crusher. 

It  is  obviously  impossible  to  lay  down  any  hard  and  fast 
rule  for  the  spacing  of  drill  holes.  In  stratified  rock  that  is 
friable,  and  in  traps  that  are  full  of  natural  joints  and  seams, 
it  is  often  possible  to  space  the  holes  a  distance  apart  some- 
what greater  than  their  depth,  and  still  break  the  rock  to 
comparatively  small  sizes  upon  blasting.  In  tough  granite, 
gneiss,  syenite  and  in  trap  where  joints  are  few  and  far 
between  the  holes  may  have  to  be  spaced  3  to  8  ft.  apart, 
regardless  of  their  depth,  for  with  wider  spacing  the  blocks 
of  stone  thrown  down  by  blasting  will  be  too  large  to  handle 
with  ordinary  appliances.  The  mica-schist,  or  gneiss,  of 
Manhattan  Island  is  a  good  example  of  rock  that  requires 
close  spacing  of  holes  regardless  of  depth.  I  have  seen  holes 
in  it  20  ft.  deep  and  only  4  ft.  apart. 

The  effect  of  spacing  of  holes  upon  the  cost  of  excavation 
is  best  shown  by  tabulation  of  the  feet  of  hole  drilled  per 
cubic  yard  excavated,  as  shown  in  Table  XXIV. : 
TABLE  XXIV. 

Distance  apart  of  holes,  ft.   i  1.5       2  2.5       3  3.5       4          4.5       5 

Cu-  yds  per  ft.  of  hole...  0.04  0.08  0.15  0.23  0.33  0.45  0.59  0.75  0.93 
M.  of  hole  per  cu.  yd 27.0  12.0  6.8  4.3  3.0  2.2  1.7  1.33  1.08 

Distance  apart  of  holes,  ft.  6  7          8          9         10         12         14         16        18 

Cu.  yds.  per  ft.  of  hole...  1.33  1.80  2.37  3.00  3.70  5.32  7.25  9.5212.05 
Ft.  of  hole  per  cu.  yd 0.75  0.56  0.42  0.33  0.27  0.19  0.14  o.n  0.08 


218        ROCK  EXCAVATION— METHODS  AND  COST. 

Since  in  shallow  excavations  the  holes  can  seldom  be  much 
farther  apart  than  i  to  il/2  times  their  depth,  we  see  that  the 
cost  of  drilling  per  cubic  yard  increases  very  rapidly  the 
shallower  the  excavation.  Thus  an  excavation  2  ft.  deep, 
with  holes  2  ft.  apart,  requires  4.3  ft.  of  drill  hole  per  cubic 
yard,  as  against  0.42  ft.  of  hole  per  cu.  yd.  in  a  deeper  exca- 
vation where  drill  holes  are  8  ft.  apart.  Failure  to  consider 
this  fact  ruined  one  contractor  on  the  Erie  Canal  deepening, 
where  rock  excavation  was  only  2  ft.  deep.  Furthermore, 
as  we  have  seen  in  Chapter  V.,  the  cost  of  drilling  a  foot 
of  hole  is  much  increased  where  frequent  shifting  of  the  drill 
tripod  is  necessary. 


Fig.  31,  Plan. 


Fig.    32,    Profile. 


Sometimes  granites  and  traps,  even  though  tough,  will 
break  up  under  the  blast  for  several  feet  back  of  the  last  row 
of  drill  holes.  Fig.  31,  for  example,  shows  a  trap  rock  quarry 
in  which  the  holes  averaged  10  ft.  apart  and  14  ft.  deep,  but 
the  rock  was  full  of  joints  and  broke  readily,  as  is  indicated 
in  Fig.  32,  which  shows  that  the  rock  broke  3  to  4  ft.  be- 
yond the  drill  holes  when  the  dynamite  exploded.  Sedimen- 
tary rocks  often  break  for  much  greater  distances  back  of 
the  last  row  of  holes ;  and  this  is  especially  so  when  the  holes 
have  been  sprung  and  charged  heavily  with  black  powder. 
The  higher  grades  of  dynamite  are  more  shattering  in  the 
immediate  vicinity  of  the  drill  holes,  but  are  not  so  apt  to 
break  the  rock  up  a  short  distance  away.  Joveite  of  the 
same  strength  as  dynamite  appears  to  be  somewhat  slower, 
in  consequence  of  which  it  shatters  the  rock  for  a  greater 
distance  from  the  hole. 


OPEN  CUT  EXCAVATION.  219 

By  observing  carefully  the  appearance  of  rocks  in  differ- 
ent localities  it  is  possible  in  a  short  time  to  become  toler- 
ably proficient  in  the  art  of  estimating  the  probable  distance 
apart  that  holes  must  be  drilled  for  the  best  effect  with  given 
charges  of  given  kind  of  explosive ;  and  with  this  end  in 
view  a  young  man  should  avail  himself  of  every  opportunity 
of  studying  prevailing  practice  in  spacing  drill  holes  in  dif- 
ferent localities. 

Cost  of  Quarrying  Trap  for  Macadam. — The  following  is. 
an  average  of  the  cost  of  quarrying  in  several  different  trap 
quarries,  taken  from  my  own  records.  The  trap  was  hard 
to  drill,  being  seamy,  but  in  consequence  of  its  seaminess  it 
broke  up~well  when  75  per  cent,  dynamite  was  used.  Holes 
averaged  14  ft.  in  depth,  and  three  of  these  holes  per  day 
of  10  hrs.  were  drilled  with  a  3%-in.  drill  using  steam  from 
a  portable  boiler.  The  cost  of  operating  the  drill  was : 

i  driller $3.00 

i  helper 2.00 

i  fireman 2.00 

*2O  bits  sharpened  at  5  cts i.oo 

1/3  ton  soft  coal    1.25 

Hauling  water  for  boiler 75 

Oil  and  waste 25 

Drill  interest  and  maintenance 75 

Boiler       do  i.oo 


Total    $12.00 

The  wages  paid  were  high,  and  the  number  of  feet  drilled 
low,  so  that  the  cost  of  drilling  was  nearly  30  cts.  per  ft.  of 
hole.  It  required  about  0.35  ft.  of  hole  per  cu.  yd.  of  rock 
(solid  measure),  so  that  the  cost  was  10  cts.  per  cu.  yd.  for 
drilling.  Common  laborers,  at  $1.50  a  day,  sledged  the  rock 
to  sizes  that  would  enter  a  9  x  i6-in.  crusher,  and  threw  the 
stone  back  away  from  the  quarry  face  ready  to  be  loaded 
and  hauled  to  the  crusher.  Much  of  the  rock  was  already 

*  At  a  custom  blacksmith  shop  near  the  work. 


220        ROCK  EXCAVATION— METHODS  AND  COST. 

broken  small  enough  by  the  blast,  so  that  a  man  averaged 
yl/2  cu.  yds.  (solid)  a  day  sledged  and  thrown  back.  The 
items  of  cost  per  cu.  yd.  (solid)  were  as  follows: 

Cts.  per 
cu.  yd.  (solid). 

Stripping    5 

Drilling     10 

Sledging     20 

Dynamite  (75  p.  c.),  1/B  Ib.  at  25  cts.  in  the  hole.   5 

Total 40 

This  is  the  cost  per  cu.  yd.  solid  (not  including  loading 
and  hauling  away),  but  I  cu.  yd.  solid  makes  about  1.7  cu. 
yds.  when  broken ;  hence  the  cost  of  quarrying  was  about 
24  cts.  per  cu.  yd.  measured  after  breaking.  In  loading  this 
broken  stone  into  carts  one  man  would  load  about  15  cu. 
yds  .(measured  loose)  per  day.  A  man  will  load  into  wheel- 
barrows and  wheel  a  distance  of  100  ft.,  dump  and  return, 
at  the  rate  of  10  cu.  yds.  (measured  loose)  per  day.  Fur- 
ther data  on  the  cost  of  transportation  will  be  found  in  Chap- 
ter X.  It  will  be  noted  that  these  data  apply  to  quarrying 
on  a  small  scale,  with  a  portable  plant,  in  tough  rock,  but 
that  the  rock  was  seamy  and  the  face  fairly  high  (14  ft.),  as 
shown  in  Fig.  32.  Two  men  pumping  out  drill  holes  and 
carrying  dynamite  to  two  men  charging  consumed  an  hour 
in  charging  six  holes  with  50  Ibs.  of  dynamite,  or  at  the 
rate  of  12^2  Ibs.  per  man  per  hour,  or  about  iJ/£  cts.  per  Ib. 
of  dynamite  for  charging,  tamping  and  firing. 

Cost  of  Quarrying  and  Crushing  Limestone. — I  have  had 
occasion  to  open  limestone  quarries  where  a  face  only  5  or  6 
ft.  high  could  be  worked  without  doing  a  great  deal  of  strip- 
ping. The  following  was  the  average  labor  cost  of  quarry- 
ing and  crushing  60  cu.  yds.  loose  measure,  or  35  cu.  yds.  of 
solid  rocki  per  lo-hr.  day,  the  average  being  that  of  4,000 
cu.  yds. : 


OPEN  CUT  EXCAVATION.  221 

Quarry.  Crusher  (9  x  16  ins.). 

i  driller  $2.50  I  engineer $2.50 

i  helper   1.50  2  men  feeding 3.50 

i  man  stripping  ...    1.50  6  men  wheeling 9.00 

4  men  quarrying  . .  .   6.00  i  bin  man 1.50 

i  blacksmith 2.50  i  general  foreman  .  . .  3.00 

Total $14.00  Total $19.50 

The  "four  men  quarrying"  barred  out  and  sledged  the 
blasted  stone  to  sizes  that  would  enter  the  crusher ;  the  "six 
men  wheeling"  wheeled  it  in  barrows  about  150  ft.  to  the 
crusher,  and  delivered  in  on  a  platform.  The  dynamite  used 
was  40  per  cent,  at  12  cts.  per  lb.,  and  0.4  Ib.  was  used  per 
cu.  yd.  of  crushed  rock,  or  0.7  lb.  per  cu.  yd.  of  solid  rock. 
One  electric  exploder,  costing  3  cts.,  was  used  per  pound 
of  dynamite.  A  long  ton  of  coal,  at  $2.50,  and  a  gallon  of 
oil,  at  25  cts.,  were  used  per  shift  for  both  crusher  and  drill. 
Holes  were  drilled  about  5  to  6  ft.  apart,  the  face  being 

5  to  6  ft.  high,  and  the  drill  averaged  60  ft.  per  shift.   Sum- 
marizing we  have : 

Wages  of  quarry  crew $14.00 

Wages  of  crusher  crew I9-5° 

24  Ibs.  of  dynamite  with  exploders,  at  15  cts.     3.60 

i  ton  of  coal   2.50 

i  gallon  of  oil .25 


Total      $39.85 

This  is  equivalent  to  65  cts.  per  cu.  yd.  of  crushed  stone 
measured  in  the  bins,  which  is  a  high  cost,  due  to  the  low 
quarry  face,  and  the  small  plant  operated.  Current  repairs 
to  the  drill  cost  i  ct.  per  cu.  yd.  and  the  crusher  another 
i  ct. ;  steam  hose,  drill  steel  and  sundry  supplies  cost  another 
il/2  cts.  per  cu.  yd.  of  loose  rock.  Quarry  rent  was  5  cts. 
per  cu.  yd. 

Cost  of  Pit  Mining,  Brewster,  N.  Y.— In  the  magazine, 
Stone  (New  York),  1892,  page  414,  Saunders  gives  the  fol- 


222        ROCK  EXCAVATION— METHODS  AND  COST. 

lowing  data  of  cost  of  ore  bank  blasting  in  an  open  cut  at  the 
Croton  Iron  Mines.  The  work  was  done  under  Mr.  Charles 
Vivian,  contractor,  between  July  13,  1891,  and  Jan.  5,  1892: 

Total  cu.  yds.  rock  and  ore 9>295 

Total  number  of  drill  holes . . . 238 

Total   feet  drilled .  .2,988 

Average  depth  of  hole,  ft 12.50 

Ft.  of  hole  per  cu.  yd 0.32 

Lbs.  of  52  p.  c.  dynamite  per  cu.  yd O-44 

Cost  per  cu.  yd. 

Labor  of  all  kinds .$0.613 

Explosives     .081 

Steam  for  drills 028 

Repairs  and  supplies 015 


Total ,  .$0.737 

This  cost  includes  blockholing  and  sledging  the  ore  to  7-in. 
cubes,  and  the  rock  to  lo-in.  cubes.  A  baby  drill  was  used 
for  blockholing.  Mr.  Vivian  writes  me  that  his  original 
records  have  been  lost,  so  that  the  rates  of  wages  cannot  be 
ascertained,  but  I  think  it  is  probably  safe  to  assume  that 
machine  drillers  received  about  $2.75,  and  common  laborers 
$1.25  to  $1.50  per  lo-hr.  day. 

Cost  of  Excavating  Gneiss. — I  am  indebted  to  Mr.  John 
J.  Hopper,  civil  engineer  and  contractor,  for  the  following 
data,  part  of  which  originally  appeared  in  the  magazine, 
Stone.  The  work  involved  the  excavation  of  29,295  cu.  yds. 
of  gneiss  (or  mica  schist)  at  One  Hundred  and  Twenty- 
seventh  street,  New  York  City.  The  drilling  of  the  main 
holes  was  done  with  four  3^-in.  Ingersoll  steam  drills,  and 
two  "baby  drills"  were  used  for  drilling  block  holes.  The 
average  height  of  the  lifts  was  12  to  15  ft.,  and  the  cut 
ranged  from  2  to  63  ft.  deep.  Hand  drillers  and  sledgers  re- 
ceived $2  per  lo-hr.  day ;  laborers  handling  stone  and  load- 
ing wagons  received  $1.50;  one  of  the  machine  drillers  re- 
ceived $3,  and  the  rest  of  the  drillers  received  $2.75  a  day. 


OPEN  CUT  EXCAVATION.  223 

The  baby  drills  were  used  only  on  the  largest  pieces  thrown 
down  by  the  blast;  the  ordinary  sized  stone  from  the  blast 
was  broken  up  by  hand-drilled  holes  and  by  sledges  to  sizes 
suitable  for  building  rubble  foundation  walls.  A  good  deal 
of  the  stone  was  piled  up  during  the  winter  until  it  could  be 
sold.  The  drilling  part  of  the  plant  cost  $1,800;  the  boilers, 
derricks,  hoists,  etc.,  cost  $1,080;  40  per  cent,  dynamite, 
costing  20  cts.  per  lb.,  was  used.  There  were  18,433  nn-  ft- 
of  main  holes  drilled  (not  including  block  holes)  in  exca- 
vating 29,295  cu.  yds.  of  solid  rock.  The  total  cost  of  the 
work,  including  the  plant,  cartage,  sledging,  etc.,  was  $52,- 
635.  The  itemized  cost  was  as  follows : 

Cts.  per  cu.  yd. 

Foremen  and  timekeepers   8.0 

Engineers  and  drillers 10.9 

Sledgers     38.3 

Derrickmen  and  helpers  9.6 

Labor,  loading,  etc 24.7 

Hand  drillers   11.7 

Blacksmith  and  helper   5.3 

Hauling  away  in  wagons 40.5 

Explosives     9.8 

Coal,  coke,  oil,  etc 6.0 

Repairs  to  drills i.o 

Repairs  to  boilers,  derricks.,  etc 1.2 


Total  per  cu.  yd $1.67 

Mr.  Hopper  informs  me  that  in  sound  rock  where  2O-ft. 
holes  could  be  drilled,  a  drill  would  average  70  ft.  in  10 
hrs. ;  but  in  shallow  drilling  the  drills  would  frequently  not 
average  over  25  ft.  each. 

Cost  of  Excavating  Sandstone  and  Shale. — In  excavating 
shales  and  sandstones  of  the  coal  measures  of  Pennsylvania, 
Ohio,  Virginia,  etc.,  I  find  that  holes  are  usually  20  to  24  ft. 
deep,  and  spaced  12  to  18  ft.  apart.  On  an  average  we  may 
say  that  for  every  cubic  yard  of  solid  rock  there  is  V10  lin.  ft. 


224        ROCK  EXCAVATION— METHODS  AND  COST. 

of  drill  hole,  when  cuts  are  very  wide,  covering  large  areas 
of  ground;  but  in  thorough  cuts  for  railroads  it  is  not  safe 
to  count  upon  much  less  than  2/10  ft.  of  drill  hole  per  cu.  yd. 
The  holes  are  almost  invariably  sprung  with  40  per  cent, 
dynamite  and  then  charged  with  black  powder.  As  low  as 
Vso  lb.  of  dynamite  per  cu.  yd.  may  be  used  for  springing 
holes  in  shale,  and  as  high  as  */2  lb.  per  cu.  yd.  in  sandstone 
that  is  to  be  very  heavily  loaded.  (See  page  149).  I  should 
put  the  average  at  1/20  lb.  of  dynamite  per  cu.  yd.  of  shale, 
and  Vio  lb.  per  cu.  yd.  of  sandstone.  A  very  common  charge 
is  8  kegs  (200  Ibs.)  of  black  powder  per  hole,  or  about  I  lb. 
per  cu.  yd.  in  side  cuts,  and  ij^  to  2  Ibs.  per  cu.  yd. 
in  thorough  cuts,  although  as  high  as  3  Ibs.  per  cu.  yd.  have 
been  used  in  thorough  cuts  in  sandstone  where  special  effort 
was  made  to  break  up  the  rock  to  small  sizes  for  steam 
shovel  work.  The  drilling  of  the  deep  holes  costs  not  far 
from  40  cts.  per  lin.  ft.  where  drilling  is  done  by  hand  with 
wages  at  15  cts.  an  hour,  and  it  may  be  as  low  as  12  cts.  a 
lin.  ft.  if  well  drillers  are  used.  Soda  powder  costs  about  5 
cts.  per  lb.,  and  40  per  cent,  dynamite  12  cts.  per  lb.  We 
have,  therefore,  the  following: 

Cts.  per  cu.  yd. 

Drilling  Vio  ft.  to  2/io  ft.  at  40  cts 4.0  to    8.0 

Dynamite  1/20  lb.  to  Vio  lb 0.6  to    1.2 

Powder,  I  lb.  to  2  Ibs. 5.0  to  10.0 


Total  for  loosening  the  rock  9.6  to  19.2 

The  rock  is  commonly  loaded  with  steam  shovels,  and  it 
is  not  safe  to  count  upon  more  than  500  cu.  yds.  of  shale, 
or  250  cu.  yds.  of  sandstone  per  shovel  per  lo-hr.  shift.  The 
daily  (lo-hr.)  cost  of  operating  a  shovel  will  average  about 
as  follows: 

i  foreman    $4.00 

i  engineman    3.50 

i  craneman    -. . .     3.00 

i  fireman   1.75 

6  pit  men   9.00 


OPEN  CUT  EXCAVATION.  225 

i  locomotive  driver $3-°° 

i  trainman     2.00 

4  dump  and  trackmen 6.00 

i  pumpman 2.50 

i  1/3  tons  coal,  $4,  and  oil,  25c 4.25 


Total    $39-°° 

For  plant  rental  and  repairs  from  $5  to  $15  a  day  must  be 
added,  making  a  total  of,  say,  $50  a  day,  or  a  cost  of  10  cts. 
per  cu.  yd.  for  soft  shale  to  20  cts.  for  sandstone  for  loading 
and  transporting  a  short  distance,  such  as  1,000  ft.  Where 
grades  are  steep  and  distances  long,  two  or  more  dinkey  loco- 
motives will  be  required.  The  resistances  of  rolling  friction 
and  grades  are  discussed  in  my  book  on  earthwork,  and  need 
not  be  repeated  here.  We  see  that  the  cost  of  loosening, 
loading  and  transporting  shale  from  side  cuts  may  be  as  low 
as  about  20  cts.  per  cu.  yd.,  and  sandstone  from  thorough 
cuts  may  be  as  high  as  40  cts.  per  cu.  yd.,  wages  and  prices 
being  as  above  given,  and  hand  drills  used  for  loosening. 
The  cost  of  moving  the  plant  to  and  from  the  work  is  not 
included  in  the  above  costs. 

Other  data  bearing  on  steam  shovel  work  will  be  found 
in  Chapters  X.  and  XIII.  It  is  necessary  to  study  all  the 
conditions  of  each  case  and  to  apply  the  data  given  in  va- 
rious parts  of  this  book.  I  have  merely  given  the  above  as 
an  example  of  shale  and  sandstone  excavation  on  railway 
work. 

Cost  of  Railroad  Excavation  in  Tennessee. — For  the  fol- 
lowing data  I  am  indebted  to  Mr.  Daniel  J.  Hauer,  C.  E., 
an  engineer  and  contractor  experienced  in  railroad  con- 
struction : 

"In  railroad  work  it  is  difficult  to  keep  separate  records 
of  the  cost  of  excavating  earth,  loose  rock  and  solid  rock. 
Specifications  differ  as  to  classification  of  excavated  mate- 
rials and  engineers  differ  in  their  interpretation  of  specifi- 
cations, all  of  which  must  be  borne  in  mind  when  studying 
data  of  railroad  excavation.  The  costs  that  follow  apply  to 


226        ROCK  EXCAVATION— METHODS  AND  COST. 

railroad  work  done  in  the  Cumberland  Mountains  of  Ten- 
nessee. 

Under  "loose  rock"  were  included  shale,  slate,  coal,  soft 
friable  sandstone,  cemented  gravel,  stratified  stone  in  layers 
less  than  6  ins.  thick  and  boulders  not  less  than  2  cu.  ft.  nor 
more  than  I  cu.  yd.  in  size.  Solid  rock  included  all  "rock  in 
place  which  rings  under  the  hammer,"  except  rock  in  layers 
less  than  6  ins.  thick.  The  clause  relating  to  6-in.  layers  was 
not  enforced,  but  such  rock  and  slate  were  classified  as  solid 
rock.  The  excavation  was  all  done  by  hand,  there  being  no 
power  drills  or  steam  shovels  used.  The  rock  was  hauled 
to  the  embankments  in  barrows,  carts  and  cars.  Wages 
ranged  from  $1.25  to  $1.50  per  day;  the  day  being  10  hrs. 
long  in  winter  and  n  hrs.  in  summer;  the  average  wage 
being  about  1^/2  cts.  per  hr.  Laborers  were  scarce  and 
inclined  to  be  independent.  Foremen  received  $3  a  day,  or 
an  average  of  28.6  cts.  per  hr.  Black  powder  cost  $1.22  per 
keg  (25  Ibs.)  ;  40  per  cent,  dynamite,  11%  cts.  per  Ib. ;  Jud- 
son  powder,  7^4  cts  per  Ib. ;  double  tape  fuse,  42  cts.  per 
coil  of  100  ft. ;  quintuple  caps,  75  cts.  per  100,  and  electrical 
exploders,  4  to  7  cts.  each,  according  to  lengths.  The  men 
were  worked  in  gangs  of  about  10  men  under  one  foreman, 
the  dumpmen  and  cart  drivers  being  included  in  this  num- 
ber. The  drivers'  wages  are  included  in  the  cost  of  "teams," 
there  being  one  driver  to  two  one-horse  dump  carts  on  short 
hauls,  and  one  driver  to  three  carts  on  long  hauls.  Two 
carts  and  a  driver  were  paid  $3  a  day.  When  dump  cars 
were  used,  two  cars,  one  mule  and  a  driver  were  counted 
at  $2  a  day.  By  dividing  the  number  of  loads  (tal- 
lied by  the  dumpman)  into  the  yardage  given  by  the  en- 
gineers in  the  monthly  estimates,  the  following  results  were 
obtained : 

Dump  cart,  without  tail  gate ....  Earth  0.6    cu.  yd. 
"       "     ....Rock  0.35    "     " 

Dump  car,         "         "       "     ....  Earth  i.o      "     " 
"       "         ..Rock  0.6      "     " 


OPEN  CUT  EXCAVATION.  227 

Dump  car,  with  tail  gate Earth  1.25  cu.  yd. 

«          «      «       "       "    Rock  0.7      " 

Tail  gates  were  not  used  in  carts  until  the  haul  became 
1,200  ft.  or  more;  and  tail  gates  were  not  used  in  cars  until 
the  haul  became  1,500  ft.  The  dump  car  body  held  iV2  cu. 
yds.  water  measure.  It  is  safe  to  count  upon  loads  10  to  15 
per  cent,  less  than  those  above  given ;  thus,  in  a  train  of  two 
or  three  cars,  without  tail  gates,  count  on  y2  cu.  yd.  of  solid 
rock  per  carload.  In  short  hauls,  the  driver  takes  one  cart 
or  car  to  the  dump  while  the  other  is  being  loaded. 

All  items  of  cost  are  given,  except  the  salaries  of  super- 
intendent, time  keepers,  blacksmith  and  night  watchmen; 
but  the  cost  of  these  items  was  6  per  cent,  of  the  total  cost, 
being  distributed  as  follows: 

Superintendent    . $975-5° 

Blacksmith  .-rrTTT^-r. 586.80 

Time  keeper 584-85 

Night  watchman  457-5° 


Total  $2,604.65 

Each  cut  was  opened  up  with  wheelbarrows,  and  when 
the  extreme  haul  for  these  became  50  ft.,  either  dump  carts 
or  cars  were  substituted.  The  cars  were  operated  on  wooden 
rails,  made  of  2  x  4-in.  scantlings,  either  of  oak  or  beech. 
The  entire  cost  of  these  tracks  is  included  with  labor, 
except  the  cost  of  the  two  by  fours,  which  were  used  several 
times,  these  being  only  10,000  ft.  B.  M.,  bought  at  a  cost  of 
$10  per  M.  These  tracks  worked  well  except  in  dry  weather, 
when  it  was  necessary  to  have  a  man  pour  water  on  the  rails, 
or  else  the  cars  were  frequently  derailed.  On  sharp  curves 
and- at  switches,  guard  rails  were  used. 

The  cost  of  trimming  and  dressing  up  the  work  is  included 
in  each  case  but  it  may  be  of  interest  to  consider  some  fea- 
tures of  it  separately.  All  cuts  were  excavated  a  foot  below 
the  cross-section  stakes,  and  then  this  foot  was  rilled  back, 
leaving  a  ditch  on  either  side  of  the  cut  wherever  the  plans 
called  for  one.  If  this  back  filling  was  made  from  the  cut 


228        ROCK  EXCAVATION— METHODS  AND  COST. 

no  payment  was  made  for  the  work ;  but  if  it  was  done  with 
material  from  a  borrow  pit,  it  was  paid  for  as  earth.  Blue 
prints  were  furnished  for  this  work  and  stakes  were  driven 
to  grade,  and  the  work  was  supposed  to  be  done  within  0.05 
ft.  This  method  saved  the  railroad  company  a  little  money 
in  ballasting,  but  it  added  materially  to  the  cost  of  dressing 
up  for  the  contractor.  He  was  allowed  6.6  cu.  yds.  of  earth 
on  a  10°  curve  (the  maximum  curve  used)  per  100  ft.  of 
roadbed,  for  putting  on  this  elevation.  On  lighter  curves  a 
less  amount  was  allowed.  In  nearly  all  cases  the  cuts  were 
taken  out  a  foot  below  grade,  and  the  embankments  were 
high;  yet  to  dress  up  6,300  lineal  ft.  of  roadbed  cost  $i,- 
226.14,  making  a  cost  of  0.97  cts.  per  sq.  yd.,  or  il/2  cts.  per 
cu.  yd.  of  material  moved  within  the  6,300  ft.  This  cost  is 
excessive,  especially  when  slopes  of  cuts  have  been  trimmed 
as  work  progresses,  so  that  only  the  roadbed  has  to  be 
dressed.  Such  work  should  have  been  trimmed  and  dressed 
for  less  than  y2  ct.  per  sq.  yd. 

Table  XXV.  gives  the  yardage  and  the  cost  of  excavating 
each  cut;  and  Table  XXVI.  gives  the  cost  per  cubic  yard 
for  each  class  of  material.  It  should  be  remembered 
that  wages  were  only  13^  cts.  per  hour  for  laborers,  that 
two  mules  and  a  driver  were  30  cts.  an  hour.  To  the  costs 
given  in  the  tables  6  per  cent,  should  be  added  for  superin- 
tendance  and  general  expenses.  The  "average  haul"  was 
measured  on  the  profile  from  center  of  gravity  of  cut  to 
center  of  gravity  of  fill. 

TABLE   XXV. 

Cu.  Yds. 


1 

I  

JD 
X 

w 
$96 

O  u 

-°  o 

Cy  fr, 

i-j 
$982 

V} 

03 

H 

$4O4 

3 

o 
$1,482 

jd 

1 

2,401 

II 

2,281 

1,644 

3 

r"o 
6,416 

II  
Ill 

$11 

$266 

YJ/*^*' 

$167 
$i  610 

XT'V^T' 

$46 

$27^ 

$224 

$2,158 

'**>':TJ7  A 

717 
2  6lQ 

517 
2,831 

1,234 

7,867 

IV  
V  

\p-i»  v_n_/ 

$34 

*r  ?v-/i  \f 

$278 
$359 

H^^/  O 

$36 

$112 

$348 

$521 

4*)\J  L  ^ 

1,953 

347 
596 

502 

849 

2,549 

VI. 

$10 

$180 

$36 

$244 

1,20^ 

408 

607 

2,310 

OPEN  CUT  EXCAVATION. 


229 


$185    $1,086    $196    $1,467 
$1,003    $2,483    $454    $3,940 
$322    $1,659      $48    $2,029     . 
$397    $1,924    $346    $2,667    2 
$222       $883    $225    $1,330 
$1,090    $4,978    $777    $6,845 
$23       $327     ....       $350 

TABLE  XXVI. 
Cost  in  Cent? 
per  Cu.  Yd. 

o    be 

QJ     /""^              -    -       rl 

903     1,664      i,1  69      3,736 
176        177      6,568      6,921 
815      5,960      6,775 
,043     1,504      2,934      6,481 
764       969      2,089      3,822 
868    1,117     11,676    13,661 
400       600     i  ,000 

jd 

%  ^ 

*TJ   ^i 

bo  I-M 

|| 

tJ 

3\ 

o   <-> 

o    o 

'II 

II 

4->        03 

Time  of  Year. 

II.  0 

21.9 

43-1 

922 

D 

Nov.,  Jan.,  Apr.  to  July. 

12.8 

25.6 

ISO 

D 

Summer. 

12.3 

24.6 

46.8 

350 

C 

Aug.  to  Feb. 

.... 

26.7 

50.8 

2OO 

D 

Aug. 

1  6.6 

33.2 

225 

D 

Apr.  and  May. 

5-5 

II.  0 

21.  1 

425 

D 

Aug. 

17.0 

34-0 

64.0 

450 

D 

Winter  and  spring. 

15-5 

31.0 

58.7 

300 

CandD 

Aug.  to  Dec. 

.... 

16.5 

31-8 

50 

W 

Jan.  to  Mar. 

16.5 

33-0 

62.5 

475 

CandD 

Aug.  to  July. 

12  $ 

2$  O 

47  ^ 

2^0 

Summer. 

144 

28.8 

58.4 

610 

C 

Aug.  to  Aug. 

21.8 

43-7 

.... 

So 

W 

26.7 

so.6 

u 

I 

II 

Ill 

IV 

V 

VI 

VII.  ... 

VIII.  .. 

IX 

X 

XI 

XII.  ... 

XIII.  .. 
Average 

NOTE. — The  months  given  in  the  last  column  are  inclusive.  In 
the  next  to  last  column  the  letters  denote  as  follows :  D  means  by 
dump  carts ;  C,  dump  cars ;  C  and  D,  both  dump  carts  and  cars  for 
about  equal  length  of  time;  W,  wheelbarrows. 

The  materials  encountered  in  these  13  cuts  were  as  fol- 
lows: 

Case  I.  Shale  and  slate  ledges  across  part  of  cut,  large 
and  small  sandstone  boulders,  stiff  clay  and  earth.  Work 
was  stopped  in  wet  weather  on  account  of  slides. 

Case  II.  Disintegrated  rock,  sandstone  boulders,  fire  clay 
and  earth. 

Case  III.  Slate  rock  in  masses,  shale,  sandstone  boulders 


230        ROCK  EXCAVATION— METHODS  AND  COST. 

and  earth.  A  thorough  cut  first  made,  then  borrowed  from 
the  sides.  One  mule  pulled  two  cars. 

Case  IV.  This  work  consisted  in  reducing  a  slope  that 
was  54  to  :>  making  it  I  to  I.  Sandstone  and  rotten  sand- 
stone; the  latter  pulverized  on  being  shot. 

Case  V.  This  was  a  borrow  pit  of  disintegrated  sandstone 
and  average  earth.  Some  of  this  sandstone  should  have 
been  classified  as  solid  rock. 

Case  VI.  Slate  in  masses,  fire  clay,  fire  clay  shale  and 
debris  from  old  slides  consisting  of  boulders  and  earth.  One 
foreman  handled  two  gangs. 

Case  VII.  This  was  a  borrow  pit,  material  being  same 
as  in  Case  VI. 

Case  VIII.  Solid  gray  sandstone  (seamy)  and  a  small 
amount  of  earth  and  loose  rock  at  each  end.  Thorough  cut. 

Case  IX.  This  was  a  borrow  pit  and  a  continuation  of  the 
sandstone  ledges  of  Case  VIII. 

Cases  X.  and  XI.  Mountain  debris,  consisting  of  sand- 
stone boulders  (large  and  small),  fire  clay,  cemented  gravel 
and  earth,  material  always  wet  and  heavy  to  shovel;  slides 
were  frequent  in  winter. 

Case  XII.  Half  of  this  cut  was  solid  sandstone.  At  the 
other  end  was  slate,  fire  clay  shale,  disintegrated  shale,  clay 
and  large  sandstone  boulders.  The  cut  was  27  ft.  deep  at 
deepest  point.  In  the  winter  the  shale  slid  on  the  fire  clay 
shale,  bringing  down  several  thousand  yards  of  slides  into 
the  cut.  For  five  months  (December  to  April)  the  shovelers 
stood  in  mud  and  water  above  their  ankles.  Material  would 
frequently  run  out  of  the  cars  on  the  way  to  the  dump. 

Case  XIII.  This  was  a  trench  6  ft.  deep,  20  ft.  wide  on 
top,  15  ft.  wide  on  bottom,  dug  to  carry  a  creek. 

It  is  not  possible  in  all  cases  to  compare  the  cost  of  one 
cut  with  another,  but  from  the  figures  given  several  deduc- 
tions can  be  made.  In  Cases  X.  and  XL  the  materials  ex- 
cavated were  similar.  There  was  a  difference  in  the  length 
of  the  haul,  but  the  great  difference  in  the  cost  of  the  work 
can  be  attributed  to  the  time  of  the  year  that  the  excava- 


OPEN  CUT  EXCAVATION.  231 

tions  were  made.  One  was  worked  entirely  during  the  sum- 
mer, while  the  other  was  worked  during  both  summer  and 
winter.  If  both  cuts  had  been  made  in  the  summer  months 
their  costs  should  have  been  approximately  the  same,  the 
slight  difference  in  cost  of  haul  counting  in  favor  of  the 
cut  in  Case  XL  A  valuable  lesson  can  be  learned  from 
Cases  VIII.,  IX.  and  XII.  In  these  the  greater  part  of  the 
material  was  sandstone,  being  classified  as  solid  rock.  In 
two  cases  the  work  consisted  of  thorough  cuts  and  one  a  side 
hill  borrow.  In  VIII.  the  cost  of  explosives  was  a  little 
more  than  $1,000,  while  with  nearly  twice  the  yardage  in 
XII.  the  cost  of  the  explosives  was  not  $100  more.  The 
difference  in  the  cost  of  the  teams  in  the  two  cases  is  readily 
accounted  for  when  the  lengths  of  the  average  hauls  are 
compared.  The  great  cost  of  powder  in  Case  VIII.  can  to 
a  great  extent  be  attributed  to  the  waste  of  incompetent  fore- 
men. The  majority  of  boulders  were  "mud  capped"  instead 
of  being  "blocked,"  or  having  the  charge  of  dynamite  placed 
under  the  rock.  In  all,  seven  different  foremen  worked  in 
this  cut,  four  of  whom  were  discharged  as  incompetent ;  but 
the  damage  was  then  done  and  the  money  in  part  lost.  All 
thorough  cuts  were  shot  with  Judson  powder,  as  the  rock  is 
broken  better  than  when  black  powder  is  used,  and  much 
"blocking"  of  boulders  is  prevented.  Better  results  can  al- 
ways be  obtained  with  Judson,  except  where  it  is  desired  to 
waste,  when  black  powder  should  be  used.  In  Case  VI.  Jud- 
son powder  pulverized  all  the  solid  rock,  so  that  no  "block- 
ing" was  needed,  as  all  the  material  was  easily  worked  by 
hand.  In  Case  IX.,  as  it  was  very  important  that  none  of 
the  material  should  be  wasted,  Judson  powder  was  used,  and 
less  than  $50  was  spent  in  breaking  up  boulders.  The  cost 
of  explosives  in  the  entire  borrow  was  only  4^4  cts.  per  cu. 
yd.  of  rock  moved.  In  comparing  all  the  cost  items  of  thif 
case  with  Cases  VIII.  and  XII.  the  striking  difference  in  the 
cost  of  side  hill  wcrk  and  thorough  cuts  can  be  seen. 

It  was  found  necessary  to  widen  and  lower  to  grade  cer- 
tain cuts  that  had  been  left  incompleted  by  another  contrac- 


232        ROCK  EXCAVATION— METHODS  AND  COST. 

tor.     The  cost  of  such  skimming  work  is  high,  as  is  well 
shown  in  Table  XXVII. : 

TABLE  XXVII. 

Cost  per  Cu.  Yd. 

t/j 

i  *    1     ,     II 

3  *     1      f       &         "       113 

u  u     E        w       •  j          £        ffi         g         H 

XIV 626    225    $0.098    $0.384    $0.103    $0.093    $0.001    $0.684 

XV 484      ISO  .I08  .488  .122  .O8l  .001  .800 

XVI 415    325        .095        .334        .116        .091        .024        .660 

Case  XIV.  was  a  breast  10  ft.  deep  on  the  side  of  a  cut 
in  hard  blue  sandstone. 

Case  XV.  was  the  widening  of  both  slopes  of  a  cut  in  red 
sandstone  and  the  excavation  of  the  bottom. 

Case  XVI.  was  the  excavation  of  the  bottom  of  a  cut  in 
blue  sandstone ;  at  no  place  was  the  face  excavation  more 
than  5  ft.  deep;  i^-yd.  dump  cars  were  used. 

In  cases  XIV.  to  XVI.  laborers  received  $1.50  per  10  hrs., 
and  foremen  $3  to  $3.50;  one  driver  and  two  mules  on  two 
carts  were  rated  at  $3.50  a  day;  powder  was  $1.20  a  keg,  and 
dynamite  (40  per  cent.)  was  10  cts.  per  Ib. 

Cost  of  Blasting  Boulders. — I  am  also  indebted  to  Mr. 
Hauer  for  the  following  data  on  the  cost  of  blasting  "loose 
rock"  in  railway  cuts.  So  far  as  I  know  these  are  the  only 
records  in  print  on  this  subject. 

The  bojulders  were  red  sandstone  and  blue  sandstone,  the 
latter  being  the  harder  and  tougher  of  the  two,  and  were 
all  broken  to  sizes  that  could  be  loaded  by  hand.  With 
wages  of  hand  drillers  and  sledgers  at  $1.50  for  10  hrs.,  and 
40  per  cent,  dynamite  at  10  to  13  cts.  per  Ib.,  the  costs  were 
as  follows : 

Sledging  a  i2>^-cu.  ft.  blue  sandstone  boulder  to  small 
sizes  took  I  man  5  mins.  and  2  men  2  mins.,  at  a  cost  of  4.9 
cts.  per  cu.  yd.  Sledging  a  16  cu.  ft.  blue  sandstone  boulder 
took  i  man  3  mins.,  or  i%  cts.  per  cu.  yd.  Sledging  a  12-cu. 
ft.  blue  sandstone  boulder  took  2  men  8  mins.,  or  9  cts.  per 


OPEN  CUT  EXCAVATION.  233 

cu.  yd.  Sledging  a  7^-cu.  ft.  blue  sandstone  boulder  took 
I  man  3  mins.,  or  2.7  cts.  per  cu.  yd.  Sledging  a  27-01.  ft. 
red  sandstone  boulder  took  3  men  10  mins.,  or  7^2  cts.  per 
cu.  yd.  Sledging  a  23-cu.  ft.  red  sandstone  boulder  took 
3  men  5  mins.,  or  4.1  cts.  per  cu.  yd.  Sledging  an  i8-cu.  ft 
red  sandstone  boulder  took  I  man  4  mins.,  or  il/2  cts.  per 
cu.  yd.  The  average  cost  of  breaking  up  small  boulders 
with  sledges  was  5  cts.  per  cu.  yd.  The  cost  of  mud  capping 
17  boulders  is  given  in  the  following  table,  in  which  the  first 
four  boulders  were  red  sandstone,  and  the  rest  were  blue 
sandstone : 

TABLE  XXVIII. 

~i<   en  iT  3 

3  T3  £  v>  r  ) 

°^  0  r?  U 


w 

•a 

KM 

e/j 

1 

E 

^5 

O 

i 

P 

§£ 

& 

§1 

c/5 

b 

3 

ctf 

I 

tn 
U 

1? 

i 

17.0 

30 

$2.10 

9 

14.7 

2 

1.6 

8 

2O 

2 

18 

3 

I.O 

8 

15 

2 

25 

4 

ZA 

8 

10 

2 

27 

5 

I.O 

1:? 

15 

10 

2    1 

48 

6 

1.2 

8 

20 

2 

25 

7 

1.4 

8 

25 

2 

25 

8 

o-7 

j     8 
1    ii 

10 
15 

2    [ 

68^ 

9 

0.33 

8 

7/2 

2 

52^ 

10 

i-3 

ii 

20 

2 

25/ 

ii 

0-45 

ii 

15 

2 

62.2 

12 

o.S 

ii 

15 

2 

56 

13 

0-5 

ii 

10 

2 

'46 

14 

0-5 

10 

7/2 

2 

39 

15 

10 

1754 

2 

17-3 

16 

I.O 

10 

7/ 

2 

I9/ 

17 

I.O 

IO 

I2J4 

2 

24^ 

Boulders  No.  5  and  8  were  blasted  twice.  In  addition  to 
the  cost  of  mudcapping  given  in  the  table,  the  following  was 
the  cost  per  cu.  yd.  of  sledging  boulders :  No.  5,  3  cts. ;  No. 
6,  5  cts.;  No.  7,  4  cts.;  No.  10,  6  cts.;  No.  15,  2  cts.  The 
average  cost  of  breaking  up  these  17  boulders  by  mudcap- 
ping was  36  cts.  per  cu.  yd. 

The  cost  of  blockholing  five  boulders  is  given  in  the  fol- 
lowing table,  all  boulders  except  No.  I  being  blue  sandstone : 


234        ROCK  EXCAVATION— METHODS  AND  COST. 
TABLE  XXIX. 

t£             *8*              •=!                       f£                «f  3 

S      ^      -c         u      s  3 

•C         Q   .  fe  OT- 

ij  <3  °  *s  i  i_;i  3  &- 

£   £             „-             •£  -M          .«   &>                                 en  .J2               O  13             *rt 

'*'*     S                         K»                            C^fa.,                    t/5      C                               G                             Q,f     •)                            I"V  4_i                           4_>    I 

o;  3         .N            <u  |-L^        o"^             >»            «5  ^^  o            o1 

-J^c/}QU                QO              j  HH 


1  13          3          105          20          2          18          145          ii 

2  31  40  10  2  8  60  20 

3  4^/2       il/2         52  12          2  10  76  17 

4  2^       i  30  82  5  45  18 

5  2  2/3      20          10          2  4  36          18 

The  labor  item  in  the  seventh  column  includes  the  cost  of 
lost  time  in  leaving  the  pit  during  the  blasting.  Boulders 
No.  i  and  3  were  fired  alone,  making  this  labor  item  greater 
than  in  the  other  cases  when  several  boulders  were  fired  at 
one  time. 

The  cost  of  undermining  and  blasting  sandstone  boulders 
was  as  follows:  A  5o-cu.  yd.  boulder  was  broken  up  by 
undermining  it,  charging  with  black  powder,  and  tamping 
with  a  large  quantity  of  sand  around  it,  the  total  cost  being 
25  cts.  per  cu.  yd.,  distributed  as  follows : 

4  kegs  of  powder,  at  $1.64 $6.56 

2^  Ibs.  40  per  cent,  dynamite,  at  16  cts 40 

Cap  and  fuse   04 

Labor     5.50 


Total    $12.50 

The  labor  force  was  i  foreman  at  30  cts.  an  hour,  2  labor- 
ers at  10  cts.  an  hour  and  I  boy  at  5  cts.  an  hour.  Five  other 
smaller  boulders  were  undermined  and  blasted  at  costs  given 
in  the  following  table : 

TABLE  XXX. 


Reference     Size,  Cu. 
Number.         Yds. 

Labor, 
Cts. 

Dynamite,     Cap  and      Total  per  C 
Cts.         Fuse,  Cts.     Yds.,  Cts. 

I                  O.9 

10 

5l/2                   2                   19.4 

2                    1-5 

13 

16^2                    2                    21 

3               1-25 

9 

8                 2              15.2 

4              i.o 

9 

5                 2              16 

5              2.5 

9 

8                 2               8.4 

OPEN  CUT  EXCAVATION.  235 

Boulders  No.  I  and  2  were  red  sandstone,  and  laborers 
were  paid  13^  cts.  an  hour;  40  per  cent,  dynamite,  n  cts. 
per  Ib.  Boulders  No.  3,  4  and  5  were  blue  sandstone ;  labor- 
ers were  paid  15  cts.  an  hour ;  dynamite,  10  cts.  per  Ib. 

Comparing  the  average  costs  of  breaking  up  sandstone 
boulders  by  the  four  different  methods  we  have: 

By  sledging 5  cts.  per  cu.  yd. 

By  mudcapping    36  "      " 

By  blockholing   17  "      "     "      " 

By  undermining  16  "      "     "      " 

In  none  of  the  casqs  did  the  men  know  that  they  were 
being  timed,  so  that  the  costs  may  be  assumed  as  fair  aver- 
ages. It  is  evident  that  mudcapping  should  be  used  only  in 
steam  shovel  work  through  cuts  where  boulders  must  be 
broken  up  quickly  so  as  not  to  delay  the  shovel.  To  illus- 
trate how  expensive  it  is  to  mudcap,  one  more  example  will 
serve.  In  a  cut  (approach  to  a  tunnel)  1,054  cu.  yds.  of 
solid  sandstone  were  excavated,  36  kegs  of  black  powder 
costing  $51  being  used.  In  this  same  cut  there  were  512  cu. 
yds.  of  loose  rock  (boulders)  which  were  broken  by  mud- 
capping,  requiring  750  Ibs.  of  40  per  cent,  dynamite,  costing 
$90. 

For  moving  boulders  short  distances  to  a  steam  shovel, 
to  a  derrick  or  even  to  the  dump,  a  stone  sled  (or  boat  or 
"lizard")  should  be  used.  Where  many  boulders  are  to  be 
moved  to  the  dump  use  three  sleds,  and  several  chains  for 
each  team.  Have  a  dump  crew  and  a  loading  crew,  and 
thus,  with  the  extra  sleds,  keep  the  team  moving.  Boulders 
from  y^  to  I  cu.  yd.  can  thus  be  moved  a  short  distance 
cheaper  than  by  blasting  and  loading  into  wagons.  By  hav- 
ing a  number  of  rollers  at  the  dump,  the  dump  crew  can 
work  the  sled  along  on  the  rollers,  using  bars  and  levers, 
until  it  tilts  up  at  the  edge  of  the  dump  and  discharges  its 
load. 

For  loading  large  scattered  boulders  into  wagons  use  a 
three-leg  (or  tripod)  derrick  with  a  Triplex  block,  A  "lift- 


236        ROCK  EXCAVATION— METHODS  AND  COST. 

er"  or  "devil"  is  a  simple,  handy,  device  for  loading  3  or  4 
cu.  ft  boulders  by  hand.  The  "lifter"  is  simply  a  stretcher 
made  of  two  3-in.  round  poles  8  ft.  long,  with  2-in.  plank, 
2^/2  ft.  long,  nailed  across  so  as  to  make  a  platform  on  which 
to  carry  the  boulder.  Several  men  can  thus  carry  a  j/2-cu. 
yd.  boulder.  Where  a  few  large  boulders  are  to  be  loaded 
upon  a  wagon,  take  off  the  two  wheels  on  one  side  of  the 
wagon  and  skid  the  boulders  up  into  the  wagon;  then  use 
levers  to  raise  the  wagon  axles,  and  replace  the  wheels. 

Where  many  boulders  are  to  be  loaded,  a  derrick  car  may 
be  used.  A  car  provided  with  an  A-frame  at  the  front  end, 
a  hoisting  engine,  and  light  jack  arms,  will  lift  5-ton  boul- 
ders. Such  a  car  will  cost  about  $1,000  and  the  engine  will 
cost  another  $1,000. 

When  a  steam  shovel  is  used  to  load  large  boulders  or  loose 
rock  that  will  not  pass  through  the  dipper,  use  chains.  A 
chain  should  have  a  hook  at  each  end,  and  one  hook  to 
fasten  the  boulder  and  the  other  to  hook  into  a  chain  fastened 
to  the  dipper  arm  or  to  a  chain  on  one  of  the  dipper  teeth. 
Two  small  boulders,  l/2  to  I  cu.  yd.  each,  may  be  chained 
out  at  one  time.  For  large  boulders,  i  to  3  cu.  yds.,  use  a 
chain  with  a  pair  of  grab  hooks  and  keep  one  or  more  men 
busy  drilling  dog  holes  in  the  boulders  for  the  grab  hooks  to 
bite  into.  With  a  65-ton  shovel  it  is  possible  to  load  a  4 
cu.  yd.  boulder. 

Summary. — The  two  cost  items  that  the  inexperienced 
man  should  seek  first  to  inform  himself  upon,  are :  ( i )  The 
number  of  feet  of  hole  drilled  per  cubic  yard  in  different 
kinds  of  rock;  and  (2)  the  number  of  pounds  of  explosive 
required  per  cu.  yd.  under  varying  conditions.  In  Table 
XXXI.  I  have  given  a  summary  of  these  items  as  applying 
to  open  cut  work  discussed  in  this  book ;  the  table  does  not 
apply  to  trenching,  tunneling  or  other  narrow  work.  Two 
examples  are  given  for  sandstones  and  two  for  shales,  such 
as  occur  in  the  coal  measures  of  Pennsylvania.  In  a  thor- 
ough cut  on  railroad  work,  we  have  conditions  that  ap- 


OPEN  CUT  EXCAVATION.  237 

proach  trench  work,  requiring  more  feet  of  hole  and  more 
powder  than  in  open  side  cuts ;  hence  the  differences  between 
Examples  5  and  6,  7,  and  8.  It  will  be  observed  that  the 
large  amount  of  drilling  in  Example  2  is  due  to  the  shallow- 
ness  of  the  face  or  lift,  and  in  Examples  9  to  12  it  is  due  to 
the  toughness  of  the  rock. 

I  shall  greatly  appreciate  further  contributions  of  similar 
data  from  my  readers,  for  use  in  future  editions.  The 
greater  the  number  of  records,  such  as  those  in  Table  XXXI. 
the  better  will  readers  be  able  to  judge  the  range  and  the 
average  for  each  class  of  rock. 

TABLE  XXXI. 

Per  Cu.  Yd. 

-4-T  ^  ' 

js  Q 

~         W  Q 

*&<  °  *>          O   <]j  •£ 

rt  a"1"'  °  '  °  ''5          *^^ 

W       Q  £        H-]          H-)  O  Kind  of  Rock. 

1  12       0.40       ...        0.75       40%      Limestone,  Chicago   Canal. 

2  6        i.oo       ...        0.7         40%  for  crushing. 

3  20  0.37  50%                           for  cement. 

4  15  0.43  ...  0.26  50%                            (holes  sprung). 

5  20  o.i  i.o  o.i  40%  Sandstone,  side  cut. 

6  20  0.2  2.0  0.2  40%                           thorough  cut. 

7  24  0.08  0.7  0.03  40%  Shale,  soft,  side  cut. 

8  24  0.20  1.5  o.io  40%                  hard,   thorough  cut. 

9  1 6  1.36  ...  0.20  60%  Granite,  for  rubble. 

10  12  1.33  ...  0.60  40%  Gneiss,  New  York  City. 

11  14  0.63  ...  0.50  40% 

12  12  1.7  ...  0.67  40%  Syenite,   Treadwell   mine. 

13  i2l/2  0.32  ..  .  0.44  52%  Magnetic  iron  ore. 

14  14  0.35  ...  0.20  75%  Trap,  seamy. 

15  16  i.o  ...  0.70  40%          "      massive. 


CHAPTER  XIII. 

METHODS  AND  COSTS  ON  THE  CHICAGO  DRAINAGE 

CANAL. 

General  Conditions. — The  illustrations  in  this  chapter 
originally  appeared  in  Engineering  News.  For  cost  data 
I  am  particularly  indebted  to  Mr.  W.  G.  Potter,  to  Engineer- 
ing News  and  to  Engineering  Record. 

No  excavation  work  of  such  magnitude  as  the  Chicago 
Drainage  Canal  has  ever  been  so  fully  described  in  print; 
and,  what  is  more  noteworthy,  no  such  complete  record  of 
cost  has  ever  been  published  before.  In  view  of  these  facts, 
and  because  such  a  variety  of  machines  were  used  in  exca- 
vating this  canal,  I  have  thought  it  wise  to  devote  one  chap- 
ter to  this  great  work. 

K 30f>'0" -— H 


x. 


K ZOS'O 

Chicago     Main     Drainage    Channel. 
Fig.  33- 

The  rock  section  of  the  Chicago  Canal  is  160  ft.  wide  at 
the  base,  and  has  vertical  sides  36  ft.  high.  The  rock  was 
excavated  in  three  12-ft.  lifts,  channeling  machines  being 
used  to  cut  perfectly  smooth  walls.  The  excavation  was 
classified  as  solid  rock  and  "glacial  drift" ;  the  latter  includ- 
ing all  material  other  than  solid  ledge  rock.  The  solid  rock 
was  limestone  (Niagara  period),  occurring  in  horizontal 
strata.  The  lower  lift  is  said  to  have  been  almost  twice  as 
hard  to  drill  and  channel  as  the  upper  lift.  The  contractors 
were  required  to  base  their  bids  on  the  results  obtained  by 
borings.  Mr.  L.  E.  Cooley,  the  first  chief  engineer,  in- 
tended to  sink  a  number  of  test  pits,  but  was  overruled  by 
the  first  Board  of  Trustees,  which  acted  under  the  usual 
cents  wise  and  dollars  foolish  policy  of  political  "boards." 

238 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    239 

The  borings  gave  an  entirely  misleading  idea  of  the  char- 
acter of  the  glacial  drift,  and  failed  to  indicate  that  much 
of  it  was  an  exceedingly  tough  hardpan  of  cemented  gravel, 
and  of  gravel  boulders  mixed  with  clay.  Several  contract- 
ing firms  were  ruined  by  the  subsequent  action  of  the  board 
in  refusing  to  release  them  or  to  reclassify  the  material. 

The  average  contract  price  on  the  "glacial  drift"  excava- 
tion was  30  cts.  per  cu.  yd.  and  78  cts.  per  cu.  yd.  on  the  solid 
rock.  There  were  about  26,000,000  cu.  yds.  of  "glacial 
drift"  and  12,300,000  cu.  yds.  of  rock.  The  prices  for  ex- 
cavation included  all  bailing  and  draining.  The  contracts 
contained  an  excellent  clause  that  required  that  the  work 
done  each  month  should  be  not  less  than  such  a  proportion 
of  the  whole  work  as  one  month  was  of  the  total  number 
of  months  agreed  upon  for  completion  of  the  work. 

Excavating  Very  Tough  Clay. — After  removing  the  upper 
layer  of  prairie  soil,  an  exceedingly  tough  or  "indurated 
clay"  was  encountered  that  required  blasting.  Boulders 
were  found  scattered  through  the  clay,  and  in  some  cases 
in  such  quantities  as  to  make  a  regular  hardpan,  of  which 
I  shall  speak  later.  On  one  section,  14  men  were  kept 
busy  drilling  and  blasting  for  one  Bucyrus  shovel  hav- 
ing an  output  of  only  350  cu.  yds.  per  lo-hr.  shift. 
The  shovel  took  out  a  swath  12  to  14  ft.  deep,  and  blasting 
holes  were  put  down  16  to  18  ft.  deep,  sprung  with  dyna- 
mite and  charged  with  Judson  powder.  On  another  section 
Barnhart  AA  shovels  averaged  520  cu.  yds.  per  lo-hr.  shift 
for  seven  months.  As  high  as  600  cu.  yds.  was  averaged  by 
a  Bucyrus  shovel  on  another  section,  showing  that  the  tough- 
ness of  the  material  varied  considerably.  For  data  as  to 
the  shovel  output  and  cost  in  this  clay,  the  reader  is  referred 
to  my  book  on  earthwork. 

Excavating  Hardpan. — The  worst  hardpan  encountered 
in  this  canal  work  is  shown  in  Fig.  34.  It  consisted  of 
boulders  and  stones  cemented  together  so  that  a  vertical 
face  was  left  after  blasting.  The  only  way  that  this  ma- 


240        ROCK  EXCAVATION— METHODS  AND  COST. 

terial  could  be  loosened  economically  was  by  means  of  large 
charges  of  dynamite  fired  at  the  rear  of  small  tunnels,  as 
shown.  The  contractors  who  at  first  bid  28  cts.  on  this  work 
subsequently  secured  50  cts.  a  cu.  yd.  on  a  re-letting.  On 
Section  4  of  the  canal  there  were  four  steam  shovels  ;  one  70- 
ton  Osgood,  one  6o-ton  Bucyrus  and  two  45-ton  Bucyrus. 
According  to  the  reports  of  the  canal  engineers,  for  October 


Fig.  34- 

1894,  the  Osgood  shovel  worked  27  ten-hour  shifts,  averag- 
ing 406  cu.  yds.  per  shift.  The  three  Bucyrus  shovels  aver- 
aged 760  cu.  yds.  for  the  6o-ton  shovel,  458  and  480  cu.  yds. 
for  the  two  45-ton  shovels.  The  general  daily  average  for 
the  season  was  493  cu.  yds.  per  shovel.  The  good  record 
made  by  the  smaller  shovels  as  compared  with  the  larger 
shovels  was  largely  due  to  the  fact  that -they  were  given  the 
easiest  material  to  handle,  so  that  no  conclusions  can  be 
drawn  as  to  relative  efficiencies  of  the  respective  shovels. 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    241 

This  remark  will  also  hold  true  of  most  of  the  data  that 
follow. 

The  material  was  loaded  in  3-cu.  yd.  Peteler  dump  cars, 
hauled  on  a  down  grade  in  trains  of  two  cars  by  two  horses 
to  the  foot  of  the  incline  and  hoisted  up  the  incline  by  a 
Lidgerwood  12^  x  i6-in.  double  drum  engine,  or  by  a  13  x 


Fig.  35. 

i6-in.  double  drum  Webster,  Camp  and  Lane  engine.  Fig. 
35  shows  one  of  these  inclines.  It  was  found  that  750  ft.  was 
the  limit  of  economic  haul  from  the  shovel  to  the  foot  of 
each  incline.  Hence  the  glacial  drift  was  taken  out  of  the 
canal  for  a  stretch  1,500  ft.  long  before  moving  the  incline. 
Fig.  36  shows  the  track  arrangement. 


242        ROCK  EXCAVATION— METHODS  AND  COST. 

For  Section  3  the  track  layout  is  shown  in  Fig.  37.  A 
Mundy  6o-H.  P.  hoisting  engine  hauled  two  3-01.  yd.  cars 
at  a  time  up  the  incline,  and  a  team  of  horses  then  hauled 
the  cars  to  the  dump.  A  team  can  haul  4  to  6  empty  cars 


Method                                             Glacial  Drift.    * 
of  Working  Rock. 

^DgjSJsSzsljC 

Fig.  36. 

<!*»*"nr^^ 

*3»*!r«tf_  Sta*S**rf       1^ 

*sr 

fc- 

Dump  for  CaUtm 

Ei  ri«t  — 

Sw//6ra 

£                c= 

v« 

:  a 

a  A 

rinqPlmt 

E            3 

r  Compressor  Plan 

5 
1 

Fig.  37- 

back.    A  Victor  shovel  was  used  on  this  work  and  its  out- 
put by  months  was  as  follows : 

Cu.  yds. 

Month.                                  Shifts.  per  shift. 

Sept.,  1894 21  362 


Oct. 

Nov. 

Dec. 

Jan., 

May 

June 

July 


24 
18 

17 

22 

21.6 

21 


333 
392 

235 
296 

380 

330 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    243 

Incline  and  Tipple. —  On  Section  I  an  incline  with  tipple 
was  used  for  handling  rock,  and  this  was  the  only  instance 
where  this  device  was  used  for  other  material  than  earth. 
The  incline  is  of  steel,  with  the  track  rising  at  a  30°  slope. 
There  is  a  trestle  approach  to  the  tipple  consisting  of  short 
king  post  spans  supported  on  trestle  bents,  which  in  turn 
rest  on  greased  skids  so  that  they  may  be  slid  along.  Fig. 
38  shows  the  arrangement  of  the  inclines  and  track  system 
for  the  rock  work,  also  the  two  derricks  carrying  the  air- 
hoists used  in  loading  large  rocks  into  the  cars.  Fig.  39 


End   Elevation. 


Side  Elevation. 


Fig.  39- 


shows  a  derrick  and  two  air  hoists  attached  to  two  horizontal 
booms  that  swing  right  or  left  so  as  to  cover  the  face  of  the 
quarry.  The  air  hoist  may  be  moved  back  or  forward  along 
the  boom.  Each  hoist  has  a  12-in.  cylinder  8  ft.  long  that  is 
supplied  with  air  from  the  compressor  on  the  framework 
as  shown.  The  compressor  which  has  an  18  x  24-in.  piston 
also  supplies  air  to  the  drills.  Six  men  operate  the  air  hoists 
on  each  face  changing  from  one  hoist  to  the  other,  so  that 
after  loading  the  large  stones  on  the  right  side,  they  move 


244        ROCK  EXCAVATION— METHODS  AND  COST. 

to  the  left  hoist,  leaving  the  right  side  free  for  men  to  load 
the  small  stones  by  hand  into  the  cars.  Two  sets  of  chains 
and  grab  hooks  were  used  with  each  hoist,  two  men  handling 
each  set  of  grabs.  While  the  hoist  is  traveling  along  the 
boom  to  the  car  one  pair  of  chainmen  are  hooking  on  to  a 
rock  at  the  face,  and,  while  the  empty  hoist  is  returning,  the 
other  two  chainmen  are  unhooking  from  the  rock  on  the 
car  and  returning.  On  man  runs  the  hoist  and  one  tagman 
swings  the  boom  and  pulls  the  hoist  back  and  forth.  The 
cars  when  loaded  are  hauled  by  mules  to  the  turn  tables, 
shown  in  Fig.  38,  where  they  are  transferred  to  the  incline 
track,  hauled  up  by  a  cable  and  dumped  by  the  automatic 
tipple.  The  cars  are  of  steel,  open  at  the  front  end,  and  there 
is  one  car  to  each  of  the  nine  tracks. 

The  output  of  the  two  incline  conveyors  was  as  follows: 

No.  lo-hr.  Cu.  yds.  solid 

shifts.  rock  per  shift. 

May    38  166 

June   67  160 

July  91  164 

Aug 97  187 

Cost  by  Lidgerwood  Cableway. — Nineteen  cableways  were 
used  on  the  canal,  spans  550  to  725  ft.  with  traveling  towers 
73  to  93  ft.  high.  Mr.  Charles  H.  Locher,  of  the  contracting 
firm  of  Mason,  Hoge  &  Co.,  invented  an  aerial  dump,  by 
means  of  which  the  skips  could  be  dumped  automatically. 
This  device  insured  the  success  of  the  cableway.  Fig.  40 
shows  the  traveling  towers.  There  are  5  cables.  The  main 
cable  for  the  carriageway  is  2^4  -ins.  diam.  and  has  a  sag  of 
5  ft.  per  100  ft.  The  hauling  cable  and  the  hoisting  cable 
are  each  %  m-  \  the  button  cable,  for  distributing  and  sup- 
porting the  fall  rope  carriers  is  ^  in.,  as  is  also  the  dump- 
ing cable  for  dumping  the  load.  The  life  of  the  main  cable 
was  50,000  to  80,000  cu.  yds.  of  solid  rock,  or  30,000  to 
50,000  trips,  or  100  to  160  days.  A  7O-H.  P.  boiler  and  a 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    245 


246        ROCK  EXCAVATION— METHODS  AND  COST. 

10  x  12-in.  engine  operate  the  cableway,  giving  a  hoisting 
speed  of  250  ft.  and  a  traveling  speed  of  1,000  ft.  per  min. 
For  shifting  the  towers  a  small  hoisting  engine  on  each  tower 
car  operates  a  system  of  blocks,  as  shown  in  Fig.  40.  The 
total  weight  of  cables,  cars,  skips  and  all  is  about  450,000 
Ibs.,  and  the  cost  about  $14,000.  Large  stones  (6  to  8  tons) 
are  chained  out  during  the  noon  hour.  The  skip  is  2  x  7  x  7 
ft.  of  ^4-in.  boiler  plate,  weighs  2,300  Ibs.  and  holds  1.9  cu. 
yds.  of  solid  rock,  although  1.6  cu.  yds.  was  the  average 
load.  The  force  consists  of  an  engineman,  a  fireman,  a  sig- 
nalman and  a  "rigger"  who  attends  to  oiling  and  changing 
worn  out  parts,  beside  men  loading  skips.  The  efficiency 
has  ranged  from  300  to  450  cu.  yds.  of  solid  rock  per  10  hrs., 
handled  at  a  cost  of  28  to  30  cts.  per  cu.  yd.,  including  load- 
ing skips,  pay  of  cableway  crew,  coal,  oil,  repairs  and  main- 
tenance, but  no  rental  for  plant.  Wages  for  lo-hr.  shift 
were  as  follows  :  Laborers,  $1.50;  foremen,  $3  ;  engineman, 
$2.75;  fireman,  $1.80;  towerman,  $2.70.  The  fireman  and 
towerman  worked  12  hrs.  when  two  lo-hr.  shifts  were 
worked  each  24-hr,  day.  The  following  is  the  record  for  the 
month  of  March,  1895,  on  Sections  2  and  4  for  four  cable- 
ways,  each  cableway  having  10  skips : 

No.   of  cableway 1234 

No.    lo-hr.   shifts 49  35  52  49 

Total  cu.   yds.   rock 12,633  8,632  16,162  14,535 

No.  skip-load  by  day  shift 5,111  5,327  5,435  4,369 

No.  skip-load  by  night  shift 4,087  1,201  5,467  4,468 

Cu.  yds.  solid  rock  per  skip 1.44  1.32  1.48  1.65 

Cu.  yds.  solid  rock  per  shift 258  247  311  297 

No.   of  laborers 27  27  32  32 

No.  of  foremen 2222 

Total  hours  labor 12,861  9,608  17,075  15,227 

Cu.   yds.    rock   loaded   per   man    per 

•shift    9.82  8.98  9.46  954 

Tons  coal  per  shift 1.83  1.83  2.28  2.28 

The  contractors,  McArthur  Bros.,  furnished  the  foregoing 
data,  also  a  table  of  percentages  of  cost,  from  which  the  fol- 
lowing has  been  compiled  by  the  author ; 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    247 
Percentages  of  Cost. 


O  «-    -l-i 

\D  3    <U  ^j 

boU~C 


'Hi  *rt 

»Q  CX  -M 

J          Z         $ 

Drilling    22      •         10  18  9.0 

Explosives     3  58  21  10.5 

Loading    46  2  31  15.5 

Conveying   15  20  17  8.0 

Channeling    4  3  4  2.0 

Pumping    4  7  5  2.5 

Supt.  and  gen'l  labor  6  . .  4  2.0 

Total 100  100  loo  50.0 

While  the  contractors  did  not  care  to  give  out  the  cost  in 
cents  for  each  item,  the  author  has  deduced  (algebraically 
from  the  data  upon  which  the  above  table  is  based)  that  on 
one  section  of  the  canal  the  total  labor  cost  two-thirds  and 
the  total  supplies  one-third  of  the  cost  of  rock  excavation, 
while  on  another  section  the  total  labor  was  60  per  cent,  and 
the  total  supplies  40  per  cent,  of  the  grand  total  cost.  Dur- 
ing the  months  of  May,  June  and  July  these  same  cableways 
on  Sections  2  and  4  averaged  340  cu.  yds.  each  per  10- 
hr.  shift. 

On  Section  3  the  output  of  four  cableways,  as  given  by 
the  Supt.  of  Construction,  was  as  follows : 

No.  ro-hr.         Cu.  yds.  per 
shifts.  shift. 

Sept.,  1894 126  294 

Oct.        "      140  267 

Nov.  153  230 

Dec.       "      140  305 

Jan.,    1895   173  161 

May  193  306 

June  181  308 

July     "     185  254 

The  contractors,  Oilman  &  Co.,  gave  the  following  as  the 
output  for  May,  which  agrees  very  closely  with  the  output 


248        ROCK  EXCAVATION— METHODS  AND  COST. 

given  by  the  superintendent  of  construction:  The  average 
output  working  two  lo-hr.  shifts  daily  was  305.3  cu.  yds. 
per  shift  per  cableway,  skips  averaging  1.6  cu.  yds.  each ;  one 
cableway  averaged  as  high  as  346  cu.  yds.  and  as  low  as  284 
cu.  yds.  Assuming  36  laborers  loading  the  9  skips  at  each 
face  (under  one  foreman),  the  average  output  per  man  per 
lo-hr.  shift  was  8.5  cu.  yds.  for  the  month  of  May.  No  de- 
lays are  counted  out,  unless  the  men  are  actually  laid  off 
without  pay;  these  delays  for  repairs  and  due  to  slight  ac- 
cidents were  probably  not  less  than  10  to  15  per  cent,  of  the 
working  time  where  two  shifts  were  worked.  Three  Rand 
drills  worked  on  each  cableway  face,  receiving  air  from  an 
18  x  3O-in.  duplex  compressor.  A  single  row  of  holes  across 
the  canal  was  exploded  at  each  blast ;  about  500  Ibs.  of  dyna- 
mite per  day  being  used  on  each  face.  Drilling  cost  6  cts. ; 
dynamite  and  blasting,  9  cts. ;  channeling,  7  cts.,  and  dump- 
ing, 2  cts. ;  total,  24  cts.  per  cu.  yd.  Assuming  36  laborers, 
at  $1.50,  loading  skips,  2  foremen  at  $3  and  cable  force  at  $7, 
2  tons  coal  for  cableway  at  $2,  we  have  a  total  of  $71  per 
lo-hr.  shift  for  loading  and  conveying,  say,  270  cu.  yds.,  or 
27  cts.  per  cu.  yd.,  which,  added  to  the  24  cts.  above  given, 
makes  51  cts.  per  cu.  yd.  exclusive  of  plant  installation,  plant 
rental  and  office  expenses. 

On  Section  6  four  cableways  were  used,  and  according  to 
the  contractors,  Mason,  Hoge  &  Co.,  the  output  was  as 
follows  for  December,  1894,  to  March,  1895: 

if  Delay  for         £  &  £  £ 

|     3      t      <     ^      a       & 

C/5  £  ^    O<  >,  *rt  " 


Dec 

Jan 

Feb 

Mar 

The  small  size  of  skip  load  is  due  to  the  large  size  of  the 
pieces.    It  will  be  seen  from  the  above  tabulation  that  from 


w 

bc»- 

S 

en 

cii 

^A      (U 

^ 

ro 

6 

J 

Pi 

in 

u 

6" 

6^ 

82 

9 

37 

138 

333 

1-30 

9.5 

99 

9 

62 

197 

338 

1-43 

9.62 

70 

9 

28 

102 

293 

1-33 

8.37 

92 

10 

91 

I4O 

345 

1.50 

9.86 

METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    249 

2  to  3  hrs.  were  lost  through  delays  during  each  lo-hr.  shift 
for  the  four  cableways,  or  an  average  of  nearly  40  mins. 
each  lo-hr.  shift  for  each  cableway.  Other  records  bear  out 
this  ratio,  as  on  Section  7  where  for  one  cableway  the  aver- 
age delay  per  lo-hr.  shift  was  1.08  hrs.  for  a  3  mos.  run, 
and  on  Section  8  a  similar  average  was  1.12  hrs.  lost  per 
shift.  In  these  cases  cableways  were  not  working  night 
shifts,  so  that  the  conditions  were  favorable.  The  Lidger- 
wood  Manufacturing  Co.  calls  attention  to  the  fact  that  the 
delays  are  due  to  two  items :  ( I )  Delay  for  repairs  to  cable- 
way;  (2)  delay  due  to  water  in  the  pit,  absence  of  rock 
ready  to  load,  and  the  like.  The  first  item,  they  claim,  is 
generally  about  one-quarter  of  the  entire  delay,  and  they 
enumerate  such  items  as  the  following:  Door  ring  leaked 
during  the  night  and  boiler  had  to  be  refilled ;  bolt  broke  in 
dumping  device ;  main  cable  sheave  broke ;  dump  line  broke ; 
dump  line  and  hoist  line  tangled ;  box  of  tower  sheave  broke ; 
button  line  broke.  In  this  way  nearly  13  hrs.  were  lost  one 
month,  while  16  hrs.  more  were  lost  waiting  for  stone  on 
Section  7,  where  due  to  these  delays  and  others  the  average 
output  for  the  month  was  403  cu.  yds.  per  shift  worked,  or 
476  cu.  yds.  per  10  hrs.  actually  run;  and  the  month  follow- 
ing the  output  was  462  cu.  yds.  per  shift  worked,  or  nearly 
500  cu.  yds.  per  10  hrs.  actually  run. 

On  Section  7  nine  skips  and  about  35  men  were  worked  on 
a  face.  About  1^/2  tons  of  coal,  costing  $2  per  ton,  and  25 
cts.  worth  of  oil  were  consumed  per  shift.  According  to 
official  report  the  average  output  of  one  cableway  for  sev- 
eral months  was  332  cu.  yds.  per  lo-hr.  shift,  but  the  con- 
tractors give  an  average  output  of  394  cu.  yds.  per  lo-hr. 
shift  for  three  months  (Jan.,  Feb.,  Mar.,  1895),  the  average 
skip  load  being  1.87  cu.  yds.,  and  the  average  lo-hr.  output 
of  each  man  loading  skips  being  10.1  cu.  yds.,  assuming  35 
men  to  have  been  the  loading  force.  As  a  matter  of  f.ict, 
they  worked  only  9-hr,  shifts,  but  for  sake  of  uniformity 
the  output  has  been  reduced  to  a  lo-hr.  basis.  The  average 


250        ROCK  EXCAVATION—  METHODS  AND  COST. 

lost  time  was  13  per  cent,  in  Jan.,  12  per  cent,  in  Feb.  and 
6  per  cent,  in  March. 

On  Section  8  a  row  of  20  holes  is  drilled  8  ft.  back  from 
the  face,  and  8  ft.  apart,  each  hole  being  loaded  with  15  Ibs. 
of  40  per  cent,  dynamite,  breaking  28  cu.  yds.  of  solid  rock. 
As  a  consequence  of  this  close  spacing  of  holes,  the  rock  was 
loosened  in  smaller  sizes,  and  each  skip  load  was  correspond- 
ingly increased.  Nine  skips  and  40  men  loading  were  em- 
ployed on  each  cableway.  Locher,  Harder  &  Williamson 
have  furnished  the  following  records  for  their  two  cable- 
ways  for  the  first  three  months  of  1895  : 


tfl 


~ 

ex 


3 


Jan  ........         10,485  17,475  80  37*  52.5 

Feb  ........          6,869  14,809  63  30*  51-9 

Mar  .......          8,180  13,491  64  30^          44.2 

The  January  record  on  this  section  is  excellent  and  shows 
what  may  be  done  where  the  plant  is  well  handled  and  the 
rock  well  broken  up,  so  as  to  reduce  the  delays  arising  from 
handling  large  rocks  with  grab  hooks.  The  average  skip 
load,  it  will  be  seen,  was  1.8  cu.  yds.  It  should  also  be  noted 
that  if  the  average  force  of  loaders  did  not  exceed  40  men, 
each  man  loaded  nearly  11^2  cu.  yds.  per  9-hr,  shift. 

Hullett-McMyler  Cantilever  Crane,  or  Conveyor.  —  This 
machine  resembles  the  Brown  cantilever  crane,  but  instead 
of  spanning  the  canal  it  reaches  only  to  the  center.  Indeed, 
as  first  made  it  was  designed  to  overhang  the  canal  bank 
but  10  ft.,  and  was  then  used  to  receive  its  skip  load  from 
a  McMyler  locomotive  crane  running  on  a  track  in  the  bot- 
tom of  the  canal  ;  but  this  arrangement  did  not  prove  suffi- 
ciently efficient.  Fig.  41  shows  the  general  design  of  the 
Hullett-McMyler  cantilever  crane  in  its  final  form  ;  and  Fig. 

*  Jan.,  all  g-hr.  shifts;  Feb.,  half  9-hr.,  half  xo-hr.  shifts. 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    251 


252        ROCK  EXCAVATION— METHODS  AND  COST. 

42  shows  the  arrangement  of  two  such  cranes  working  on 
opposite  sides  of  the  canal.  The  skip  is  of  steel  and  has  a 
capacity  of  3.7  cu.  yds.  water  measure,  or  i^g  cu.  yds.  of 
solid  rock.  A  9  x  12-in.  engine,  working  under  80  Ibs.  pres- 
sure and  with  200  revs,  per  min.,  does  the  hoisting.  The 
total  weight  of  the  crane  is  no  tons,  and  its  cost  is  given  at 
about  $9,000. 


Fig.  42. 

Only  two  of  these  cranes  were  used  on  the  canal  (on  Sec- 
tion 7).  The  daily  (lo-hr.)  expense  of  operating  each  was: 

i  engineer $2.50 

i  fireman 1.50 

Machinist  service i.oo 

Superintendence    75 

i  y\  tons  coal 2.50 

Oil  and  waste 25 

Repairs   (?)    50 

Track   maintenance 1.50 

Night  watchman    50 

Total      $11.00 

The  two  cantilever  cranes  handled  168,470  cu.  yds.  solid 
rock  in  337  lo-hr.  shifts,  or  250  cu.  yds.  per  shift  per  ma- 
chine. 

Hullett-McMyler  Derrick. — These  derricks  were  at  first 
placed  in  the  bottom  of  the  canal,  but  were  afterward  en- 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    253 

larged  and  placed  on  the  berm,  Fig.  43.  No  locomotive  crane 
had  ever  before  been  made  with  so  long  a  boom.  The  der- 
rick handles  a  skip  weighing  2,400  Ibs.,  making,  with  its  full 
load  of  i^s  cu.  yds.  solid  rock,  3^  tons  loaded.  The  ma- 
chine was  designed  to  handle  safely  a  load  of  10,000  Ibs. 
The  derrick  weighs  95  tons,  and  its  cost  is  given  at  $15,000. 


Fig.  43- 

A  cranesman,  a  fireman,  a  man  to  trip  skips,  3  laborers  hook- 
ing and  unloading  skips,  25  loaders  and  a  foreman  con- 
stitute the  crew  for  each  derrick.  The  cost  of  operation  is 
practically  the  same  as  for  the  Hullett-McMyler  conveyor. 

In  the  pit  3  men  were  busy  hooking  and  unhooking  skips 
of  which  there  were  5  or  6  to  each  machine.  The  highest 
daily  output  of  which  record  is  given  was  made  Mar.  18, 
1895,  when  605  skips,  or  980  cu.  yds.,  of  solid  rock  were 
conveyed  in  10  hrs.  by  the  two  machines.  To  load  this  rock 


254       ROCK  EXCAVATION— METHODS  AND  COST, 

there  were  59  laborers  in  the  pit,  so  that  each  man  handled 
1 6.6  cu.  yds.  that  day.  All  told,  these  two  conveyors  moved 
279,300  cu.  yds.  in  492  lo-hr.  shifts,  averaging  568  cu.  yds. 
(284  cu.  yds.  each)  per  shift. 

Geraldine  Double-Boom  Derrick. — Four  of  these  derricks 
were  used  on  the  canal,  the  general  appearance  of  each  being 
shown  in  Fig.  44.  The  derrick  revolves  on  a  turntable,  hav- 
ing a  rack  28  ft.  diam.  in  which  two  pinions  mesh  and  are 


Fig.  44. 


rotated  by  two  8  x  8-in.  vertical  engines.  The  apex  of  the 
tower  is  113  ft.  above  the  track.  The  booms  are  155  to  164 
ft.  long,  and  each  boom  carries  two  fall  blocks  for  lifting 
the  skips.  While  one  boom  overhangs  the  canal  the  other 
overhangs  the  spoil  bank.  As  soon  as  two  skips  are  hooked 
on  in  the  pit  the  engineman  begins  to  raise  them,  and  at  the 
same  time  to  swing  the  derrick.  The  skips  upon  reaching 
a  certain  height  are  dumped  automatically.  Hoisting  is  then 
stopped,  while  the  opposite  skips,  which  have  been  lowered, 
are  unhooked  and  loaded  skips  hooked  on.  Twelve  skips 
holding  2  cu.  yds.  each  are  used.  The  cost  of  operation  is : 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    255 

50  laborers  at  $1.50 $75-°° 

2  foremen  6.00 

i  engineman   2-5° 

1  fireman 1-5° 

2  trackmen   3-°° 

2  tons  coal 4-°° 

Oil,  water,  watchman  and  supt 5.00 

Total $97.00 

The  output  of  four  derricks  for  5  mos.  ending  July,  1895, 
was  300  cu.  yds.  solid  rock  per  derrick  per  lo-hr.  shift,  which 
would  indicate  that  there  were  many  delays,  since  if  50  men 
were  engaged  in  loading  the  300  cu.  yds.  the  average  per  man 
must  have  been  only  6  cu.  yds.  The  best  average  for  any 
one  of  these  derricks  for  one  month  of  this  time  was  439  cu. 
yds.  per  lo-hr.  shift. 

The  Brown  Cantilever  Crane. — The  cantilever  crane  manu- 
factured by  the  Brown  Hoisting  &  Conveying  Co.,  of  Cleve- 
land, Ohio,  had  been  used  for  many  years  for  handling  iron 
ore,  coal,  etc.,  along  the  Great  Lakes  and  elsewhere,  so  that 
its  success  on  the  Chicago  Canal  might  have  been  regarded 
as  a  foregone  conclusion.  However,  the  output  of  this  de- 
vice and  its  general  efficiency  far  exceeded  expectations.  Al- 
together eleven  of  these  cranes  were  used  on  the  canal,  and 
after  the  first  year  a  monthly  output  of  15,000  to  16,000  cu. 
yds.,  or  600  cu.  yds.  per  lo-hr.  shift  per  crane,  was  attained ; 
in  fact,  for  a  week  one  crane  handled  892  cu.  yds.  per  10- 
hr.  shift,  or  4,845  cu.  yds.  Fig.  45  shows  the  general  de- 
sign of  one  of  these  cantilever  cranes.  The  cantilever  trusses 
have  .a  slope  of  12^°  and  are  355  ft.  from  end  to  end.  A 
carriage  or  trolley  travels  along  the  track  on  the  lower  chord 
of  the  truss,  the  hoisting  power  being  a  10^2  x  12-in.  engine 
and  a  I2O-H.  P.  boiler.  The  skip  can  be  dumped  automat- 
ically at  any  point  of  its  343  ft.  travel.  The  weight  of  the 
entire  machine  is  150  tons,  and  its  cost  about  $28,000.  Each 
skip  has  a  capacity  of  75  cu.  ft.  water  measure,  and  carries 


ROCK  EXCAVATION— METHODS  AND  COST. 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    257 

1.5  to  1.7  cu.  yds.  of  solid  rock.  The  average  traveling  speed 
of  the  skip  is  150  ft.  per  min.,  although  the  maximum  speed 
is  400  ft.  per  min.  On  Section  10  the  contractors,  E.  D. 
Smith  &  Co.,  have  furnished  the  following  record  of  output 
for  the  month  of  March,  1895,  for  one  crane  working  in  the 
lower  lift,  using  9  skips : 

Number  of  lo-hr.  shifts 25 

Output  per  shift,  cu.  yds 520 

Number  of  laborers  on  the  face 48 

Output  per  laborer  per  shift,  cu.  yds 10.4 

Av.  skip  load  of  solid  rock,  cu.  yds 1.6 

There  were  two  foremen,  one  crane  engineer,  one  fire- 
man, one  oiler  for  crane  and  one  towerman  or  operator ;  2  to 
2l/2  tons  of  coal  were  burned  per  shift.  Mr.  C.  L.  Harrison, 
the  division  engineer,  gives  the  output  of  three  cranes  on  this 
section  for  six  months  of  1895  (Feb.  to  July  inclusive)  as 
having  been  205,900  cu.  yds.  in  421  shifts  (io-hr.),  or  near- 
ly 490  cu.  yds.  per  crane  per  shift;  during  the  month  of 
April  the  average  output  for  each  of  the  three  cranes  was 
542  cu.  yds. 

On  Sections  n,  12  and  13  there  were  eight  cantilever 
cranes  operated  by  the  manufacturers,  who  sublet  the  con- 
veying of  the  loaded  rock.  These  cranes  handled  2,084,700 
cu.  yds.  of  solid  rock  in  3,609  shifts  (io-hr.),  or  very  nearly 
500  cu.  yds.  per  crane  per  io-hr.  shift.  In  the  first  12  months 
(Feb.,  1894,  to  Jan.,  1895)  the  average  output  was  485  cu. 
yds.  per  crane  per  io-hr.  shift  and  10.9  cu.  yds.  per  man 
loading  skips.  The  lost  time  per  crane  per  io-hr.  shift  for 
one  month,  of  which  record  is  given,  was  about  2  hrs.,  of 
which  about  l/2  hr.  was  due  to  the  crane  and  the  other  iy2 
hrs.  to  the  failure  of  the  contractors  to  have  stone  ready  to 
load,  which  is  probably  a  fair  average.  In  Dec.,  1895,  these 
eight  cranes  working  one  9-hr,  shift  a  day  averaged  60.5  cu. 
yds.  per  hour.  For  the  12  mos.  each  of  these  eight  cranes 
averaged  23  shifts  a  month;  in  mid-winter  working  9-hr. 


258        ROCK  EXCAVATION— METHODS  AND  COST. 

shifts,  and  in  mid-summer  n-hr.  shifts,  although  the  records 

have  all  been  reduced  to  a  lo-hr.  shift  unit. 

The  daily  cost  of  operating  each  crane  was  as  follows : 

Engineman    $3-OO 

Fireman     2.50 

Oiler    1.75 

Operator    2.75 

i  2-3  tons  of  coal  at  $1.75 3.00 

Oil,  water  and  waste  (estimated) 50 

Laying  track  (estimated) 50 


Total    $14.00 

It  will  be  seen  that  the  conveying  cost  about  3  cts.  per  cu. 
yd.,  not  including  plant  rental.  No  other  method  of  convey- 
ing equaled  this  in  point  of  low  cost  of  operation,  and  it 
should  also  be  noted  that  track  had  to  be  laid  along  only  one 
berm  of  the  canal ;  but,  on  the  other  hand,  the  price  charged 
for  a  cantilever  crane  was  considerably  in  excess  of  that 
charged  for  any  other  machine.  If  $28,000  represents  the 
price  of  each  crane  and  260,000  cu.  yds.  of  rock  were  handled 
by  each  crane,  obviously  the  contractor  would  be  compelled 
to  charge  nearly  n  cts.  per  cu.  yd.  against  the  crane,  unless 
he  could  be  sure  of  a  definite  salvage  price  for  the  crane  at 
the  end  of  the  job.  Considerations  of  this  kind  are  too  often 
overlooked  by  engineers  in  estimating  the  unit  cost  of  work. 
Cost  by  Car  Hoists. — For  conveying  rock  in  dump  cars 
there  were  three  methods  used :  No.  I,  the  fixed  incline  with 
spur  tracks ;  No.  2,  the  natural  incline  with  a  loop  track,  and 
No.  3,  the  double-hoist  and  diagonal  incline. 

Method  No.  i.  This  method  was  used  on  Sections  8,  n, 
12,  13  and  15  of  the  canal.  A  number  of  spur  tracks  were 
laid  in  the  pit  up  to  the  rock  face,  and  a  number  of  spurs 
were  laid  on  the  dump,  no  spur  being  over  150  ft.  long,  and 
all  connecting  by  switches  with  the  main  track,  which  led 
up  a  fixed  trestle  incline.  This  incline  had  a  slope  of  30°,  40 
ft.  of  it  being  in  the  canal  prism  and  85  ft.  up  on  the  berm. 


METHODS-COSTS  CHICAGO  DRAINAGE  CANAL.    259 

A  hoisting  engine  was  located  at  the  head  of  the  incline. 
Single  cars  (of  which  there  were  8),  each  holding  I  cu.  yd. 
solid,  were  loaded  by  hand,  hauled  by  a  mule  to  the  foot  of 
the  incline,  hoisted  by  the  engine  and  hauled  by  a  mule  to  the 
dump.  The  average  haul  (one  way)  from  pit  to  dump  was 
about  600  ft.  The  pit  force  was  40  to  45  men  loading,  I 
water  boy,  I  mule  and  driver,  and  I  foreman.  The  dump 


Fig.  46. 

force  was  I  hoist  engineer,  I  hoist  runner,  I  mule  and  driver, 
and  4  dumpmen.  The  incline  was  torn  down  whenever  it 
had  to  be  shifted. 

Method  No.  2.  On  Section  10  the  upper  lift  was  taken  out 
by  a  car  hoist  method  that  differed  from  all  others  in  that 


260        ROCK  EXCAVATION— METHODS  AND  COST. 

there  was  only  one  (3-ft.)  gage  track  on  the  dump,  a  loop  in 
the  pit  and  practically  no  trestling  on  the  incline.  The  empty 
cars  descended  by  gravity  around  the  loop,  as  shown  in  Fig. 
46;  and  one  incline  served  two  working  faces.  The  wedge 
of  earth  and  rock  which  was  left  to  support  the  track  on  the 
incline  was  removed  in  carts  after  the  incline  had  served  its 
purpose  and  had  been  moved.  The  main  track  on  the  in- 
cline was  150  ft.  long;  at  a  distance  of  about  75  ft.  back 
from  the  canal  it  branched,  the  two  tracks  coming  down  over 
the  berm  and  meeting  at  the  far  side  of  the  canal,  forming 
a  loop  375  ft.  long.  This  method  of  track  arrangement  gavt 
a  very  short  haul  and  the  track  was  easily  maintained.  There 
were  3  trains  of  4  side-dump  cars  each,  two  being  loaded, 
while  the  third  was  at  the  dump;  and  each  car  held  il/2  cu. 
yds.  of  solid  rock.  When  a  train  was  loaded  the  cable  was 
attached  and  it  was  hauled  up  the  incline.  The  pit  force  con- 
sisted of  35  loaders,  I  water  boy,  I  cableman,  I  switchman 
and  i  foreman.  The  dump  force  was  i  hoist  engineer  and 
4  or  5  laborers. 

£    ;ng  ~~~ . 

£»>»*  {steam  Drills  * 


Method  No.  3.  Double  Hoist  and  Diagonal  Incline. — This 
was  the  only  car  hoist  method  used  for  all  three  lifts.  A 
double  track  trestle  incline  entered  the  pit  diagonally — not 
at  right  angles  with  the  canal,  like  other  inclines.  The  two 
working  faces  were  also  diagonal,  making  an  angle  of  30° 
with  the  canal,  thus  giving  a  longer  loading  line.  The  track 
layout  is  shown  in  Fig.  47.  There  were  two  parallel  main 
tracks  on  the  incline  trestle,  each  150  ft.  long;  then  each 
track  was  300  to  800  ft.  long  in  the  pit  and  600  to  1,000  ft. 
on  the  bank.  The  average  haul  was  about  700  ft.  Two 
trains  of  12  cars  each  were  used  on  each  face,  so  that  there 


METHODS—  COSTS  CHICAGO  DRAINAGE  CANAL.    261 

was  no  delay  in  loading.  There  were  sidings  in  both  pit 
and  dump.  Each  car  held  l/2  cu.  yd.  of  solid  rock.  A  double- 
drum  hoisting  engine  handled  two  cables,  one  for  each  track. 
The  pit  force  working  two  faces  consisted  of  75  loaders  and 
edgers  (i  sledger  to  6  loaders),  3  teams,  2  water  boys  and 
-  foremen.  The  dump  force  was  I  hoist  engineer,  i  firemen, 
3  teams  and  10  dump  men. 

Summary  of  Costs.  —  The  summary  in  Table  XXXII.  has 
been  compiled  by  Mr.  W.  G.  Potter.  The  wages  for  the  dif- 
ferent classes  of  workmen  are  given  elsewhere  in  this  chap- 
ter, common  laborers  in  all  cases  receiving  $1.50  for  10  hrs 
work,  all  delays  of  i  hr.  or  more  being  docked.  The  tabu- 
lated costs  do  not  include  shop  repairs,  but  do  include  field 
repairs.  The  drilling  item  appears  not  to  include  the  cost  of 
drill  sharpening.  Plant  rental  is  not  included  either  —  a  very 
important  item  where  such  expensive  machines  are  used.  Ex- 
plosives include  caps  and  dynamite,  12  cts.  per  Ib.  for  the 
40  per  cent,  dynamite  being  assumed  to  cover  the  cost  of 
explosives.  General  expenses  include  superintendence, 
watchmen  and  incidentals.  The  three  methods  of  car  hoist, 
Nos,  i,  2  and  3,  have  been  described  in  the  pages  just  pre- 
ceding. 

TABLE  XXXII. 
COST  IN  CENTS  PER  Cu.  YD.   (SOLID). 


!  .         *  i  t 

I  I  lilt  I  ! 

x  «-         xS^ 
(J 


x 
WO 


Brown  Cantilever  ----  3.9  4.1  8.O  3.2  i.o  3.6  14.6  o.o  38.3 

Lidgerwood   Cableway.  3.7  3.8  8.4  2.7  i.o  3.6  15.6  o.o  38.8 
Hullett-McMyler    Der- 

rick   .............  3.9  4.0  7.4  2.5  1.8  5.3  18.3  o.o  43.2 

Hullett    Conveyor  .....  4.1  3.7  8.5  3.8  1.2  6.2  21.4  o.o  48.9 

Car  Hoist  No.  i  ......  3.7  3.9  9.1  2.7  0.8  3.1  24.8  5.1  53.1 

Car  Hoist  No.  2  ......  3.9  3.6  8.9  3.2  0.9  1.2  22.9  2.3  47.1 

Car  Hoist  No.  3  ......  4.0  5.0  10.7  3.1  1.2  1.2  26.4  4.8  56.5 


262        ROCK  EXCAVATION—METHODS  AND  COST. 
TABLE  XXXIII. 


•o 
><  ffi 


§,£  ts 

•3  — •  o 
cj  ^  a 


Brown  Cantilever  

Lidgerwood  Cableway   . . 
Hullett-McMyler  Derrick 

Hullett  Cantilever 

Hullett    Conveyor 

Car  Hoist  No.   I 

Car  Hoist  No.  2 

Car  Hoist  No.  3 

Double  Boom  Derrick... 
St.   Paul  Derrick.. 


10 

443,750 

478 

10.45 

8 

600,725 

397 

10.25 

7 

180,406 

217 

8.52 

7 

109,397 

235 

9.91 

9 

178,839 

335 

6.85 

8 

131,674 

285 

6.96 

10 

60,341 

269 

6.98 

9 

308,531 

463 

6.82 

14 

324,880 

282 

8.22 

14 

63,700 

153 

8.22 

Cost  of  Channeling. — Channelers  had  never  been  used  on 
canal  excavations  before  the  building  of  the  Chicago  Canal. 
The  object  in  using  them  on  the  canal  was  to  secure  smooth 
side  walls  that  would  offer  little  resistance  to  the  flowing 
water.  The  limestone  varied  widely  in  hardness,  the  upper 
lift  being  as  a  rule  much  easier  to  channel  than  the  lower 
lifts.  There  were  three  lifts  of  12  ft.  each,  and  the  channel 
cut  was  offset  6  ins.  at  each  lift.  Naturally  the  lower  lifts 
were  somewhat  shattered  by  the  blasting  of  the  upper  lift, 
adding  to  the  difficulty  of  channeling.  The  average  weight 
of  a  channeler  was  11,000  Ibs. ;  it  moved  back  and  forth  on 
a  section  of  track  30  ft.  long,  striking  250  blows  per  min. 
The  width  of  the  channel  cut  by  the  bit  was  2%  ins.  at  the 
top,  decreasing  y%  in.  for  each  2  ft.  of  depth.  The  speed  of 
channeling  was  130  to  200  sq.  ft.  per  10  hrs.  on  the  upper 
lift,  and  about  half  as  much  on  the  second  and  third  lifts. 

There  were  53  Sullivan  and  33  Ingersoll  channelers.  The 
following  are  records  of  efficiency : 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    263 

Sullivan  Channeler. 

No.  101.  No.  in. 

June,        Jam,  June,          Jan., 

1893.    1894.  1893.    1894- 

No.  hours  worked 205     222  209     299 

Sq.  ft.  channeled 2,783    1,401  3,076    1,683 

Av.  sq.  ft.  per  hour 18.4     6.3  14.2     5.6 

Max.  sq.  ft.  per  day 30O1     126"  3572     96* 

Min.  sq.  ft.  per  day 90      i83  63'     I23 

1  lo-hr.  day;  2n-hr.  day;  39-hr.  day. 

Labor  troubles  in  June  reduced  the  number  of  shifts 
worked,  but  the  work  was  done  on  the  top  lift  under  the 
most  favorable  conditions.  The  work  done  in  January  was 
under  the  most  unfavorable  conditions,  on  the  third  lift, 
with  ice  and  snow,  frozen  water  pipes,  etc. ;  and  5  night 
shifts  were  worked  with  No.  in.  The  time  (hours  worked) 
is  that  for  which  the  men  were  paid,  and  includes  all  time 
lost  for  repairs  and  delays.  The  labor  and  fuel  expense  of 
running  a  channeler  was  as  follows  per  day : 

i  runner  $2-75 

i  helper 1.50 

i   fireman    1.75 

Blacksmith  and  teams  hauling  drills 70 

Superintendence  and  machinist 1.30 

1 1/4  tons  coal   2.50 


Total    $10.50 

The  Ingersoll-Sergeant  Drill  Co.  has  furnished  the  follow- 
ing record  of  work  of  5  channelers  for  the  month  of  May, 
1894,  working  on  the  top  lift:  The  average  cut  by  each  ma- 
chine for  27  working  days  was  2,279  s(l-  ft-»  or  121  sq.  ft. 
per  day.  As  high  as  221  sq.  ft.  were  cut  by  one  machine  in 
a  day,  and  the  best  of  these  5  channelers  averaged  148  sq. 
ft.  a  day  for  the  month.  The  cost  of  operation  was : 

i   runner   $3«oo 

i    helper    1.50 

i   fireman    .- 1.75 


264        ROCK  EXCAVATION— METHODS  AND  COST. 

Coal    $3.00 

Blacksmith,  machinist    1.50 


121  sq.  ft.  at  8.9  cts $10.75 

For  an  excavation  160  ft.  wide  the  cost  of  channeling,  at 
this  rate,  was  slightly  less  than  3  cts.  per  cu.  yd.  These 
figures,  however,  apply  only  to  firm  limestone  in  the  top 
lift,  and  30  to  50  per  cent,  should  be  added  to  this  cost  for 
the  lower  lifts.  Seven  channelers  on  Section  9  working  7 
mos.  in  1894  averaged  94  sq.  ft.  each  for  the  three  12- ft. 
lifts.  Lewis  gives  the  cost  of  channeling  on  Section  3  as 
being  7  cts.  a  cu.  yd.,  which  would  be  equivalent  to  about 
20  cts.  a  sq.  ft.  Engineering -News  gives  the  average  for 
the  whole  canal  work  as  8  to  10  sq.  ft.  an  hour  at  a  cost  of 
8  to  25  cts.  a  sq.  ft.,  and  places  the  average  cost  at  about  17 
cts.  a  sq.  ft.,  or  6  cts.  a  cu.  yd.  of  rock  excavated. 

Mr.  W.  G.  Potter  gives  the  following  data  for  Jan.  i, 
1894,  to  Feb.  i,  1895,  on  ten  sections: 

Section  Sq.  ft.                iJays  Cost  per  Sq.  ft. 

( 10-hr.).  sq.  ft.  per  day. 

No.  7  98,043       1,170  11.73  cts.  83.80 

No.  8  (ist  lift)..  42,000       300  7.50  "  140 

No.  8  201,558               2,339  ii. 10   "  86.2 

No.  9  182,167                1,992  12.16   "  91.4 

NQL  10 202,192               2,638  11.81    "  76.6 

Time  is  actual  working  time,  all  delays  of  i  hr.  or  more 

deducted.     Shop  repairs  are  not  included.  Wages  per  10 

hrs.  were: 

No.  7.      No.  8.        No.  9.  No.  10. 

Channelerman    $3-OO        $3-25        $3-25        $2-75 

Fireman    1-75          i-75          i-75          1-75 

Laborer    1.50          1.50          1.50          1.50 

Team    (occasional)    3-5Q          3-5O          3-5Q          3-5° 

Foreman   (for  entire  sec.) 2.75          2.75          2.75 

Coal,  oil  and  waste 1.75          2.25          2.25          1.75 

Cost  of  Drilling. — Compressed  air  was  used  on  9  out  of  15 
sections  of  the  canal.  The  common  installation  was  a  large 
compressor  located  at  the  center  of  a  section,  delivering  air 


METHODS— COSTS  CHICAGO  DRAINAGE  CANAL.    265 

at  80  to  90  Ibs.  pressure.  An  8  or  lo-in.  main  led  to  the 
canal  berm  and  there  branched,  a  6  or  8-in.  main  going  each 
way;  2-in.  feed  pipes,  175  to  230  ft.  long,  supplied  three 
drills.  The  common  size  of  drill  was  one  with  a  3^4  x  6*^- 
in.  cylinder,  and  a  2-ft.  feed  screw;  +  an<^  X-bits  were 
used,  the  X-bit  being  better.  For  a  12-ft.  hole  the  starting 
bit  was  2  ins.  diam.  According  to  W.  G.  Potter  the  expense 
per  drill  per  ic-hr.  shift  was  about  as  follows: 

Steam.  Air. 

Drill   runner    $2.00'  $2.00 

Drill  helper   1.50  1.50 

Vs   fireman    50  (air)   1.50 

Coal  and  oil 1.25  (oil)     .10 


Total     $5.25  $5.10 

On  Section  9  the  daily  average  for  6  mos.  was  82  ft.  of 
hole  per  drill  for  each  of  15  Ingersoll-Sergeant  drills;  each 
hole  being  12  ft.  deep.  Holes  were  spaced  6  to  12  ft.  apart ; 
close  spacing  decreasing  the  cost  of  sledging,*  but  increasing 
the  cost  of  drilling. 

Many  grades  of  dynamite  were  tried,  but  finally  40  per 
cent,  was  found  to  be  the  best.  The  higher  grades  shat- 
tered the  rock  in  the  immediate  vicinity  of  the  holes,  but 
threw  down  chunks  that  were  too  large  to  handle.  The 
sticks  of  dynamite  were  1^2  x  6  ins.  in  size,  weighing  £4  Ib. 
each ;  and  10  to  25  sticks  were  charged  in  a  hole,  thus  con- 
suming 0.6  to  1.2  Ibs.  of  40  per  cent,  dynamite  per  cu.  yd. 
Including  fuse  and  caps  the  dynamite  averaged  about  12 
cts.  per  Ib. 

Steam  Shovel  Output. — Steam  shovels  were  not  much 
used  for  loading  rock,  as  their  average  output  was  small. 
On  Section  15  a  20- ft.  face  was  worked,  and  5-cu.  yd.  cars 
were  loaded  by  two  Bucyrus  (55-ton)  shovels  with  broad, 
shallow  dippers  having  a  capacity  of  2^4  cu.  yds.  Cars 
were  hauled  in  trains  of  10,  one  locomotive  serving  each 


266        ROCK  EXCAVATION— METHODS  AND  COST. 

shovel.  The  best  record  made  by  one  shovel  was  600  cu. 
yds.  in  10  hrs.  The  combined  output  of  these  two  shovels 
was  as  follows: 

Cu.  Yds. 

No.  of  10-hr.        per    Shovel     Total  Cu.  Yds., 
1895.  Shifts.  per    Shift.       Solid  Measure. 

May    109  266  29.000 

June   99  291  28,850 

July    96  302  29,000 

Aug 102  310  31,800 

The  average  per  shovel  per  month  was  14,700  cu.  yds., 
working  two  shifts  a  day. 


CHAPTER  XIV. 
COST  OF  TRENCHES  AND  SUBWAYS. 

General  Considerations. — Trenching  in  rock  is  a  subject 
upon  which  practically  nothing  has  ever  been  written.  In 
consequence  there  is  probably  no  class  of  rock  work  that  is 
so  often  mismanaged ;  and,  as  a  further  consequence  of  the 
prevailing  ignorance,  engineers'  estimates  of  cost  are  often 
far  too  low  -and  occasionally  as  far  too  high.  In  city  specifi- 
cations for  sewer  trenching  in  rock  it  is  customary  to  pay 
the  contractor  only  for  rock  excavated  within  specified  "neat 
lines."  If  he  excavates  beyond  the  "neat  lines"  he  does 
so  at  his  own  expense.  In  sewer  work  the  most  common 
practice  is  to  specify  that  payment  will  be  made  for  a  trench 
12  ins.  wider  than  the  outside  diameter  of  the  sewer  pipe, 
and  6  ins.  deeper  than,  the  bottom  of  the  pipe  when  the  pipe 
is  laid  to  grade.  A  specification  should  always  name  a  mini- 
mum width  of  trench.  Some  specifications  allow  for  a  side 
batter  of  3  ins.  to  the  foot  on  each  side ;  but  unless  the  trench 
is  to  be  deeper  than  can  be  drilled  with  one  set  up  of  the  ma- 
chine drills,  and  requires  excavation  in  more  than  one  lift  or 
bench,  I  see  no  reason  for  prescribing  a  batter  to  the  rock 
sides.  The  most  rational  specification  that  I  have  seen  for 
general  use  in  rock  trenching  is  as  follows:  "All  trenches 
in  rock  excavation  will  be  estimated  2  ft.  wider  than  the 
external  diameter  of  the  pipe  and  6  ins.  below  the  sewer 
grade." 

Specifications  vary  so  widely  as  to  the  "neat  lines"  that 
bidding  prices  for  trench  work  under  different  engineers 
are  very  deceiving  to  any  one  who  has  not  studied  the  par- 
ticular specifications  covering  the  work  upon  which  the  bids 
were  made. 

Different  rocks  vary  greatly  in  the  way  the  sides  and  bot- 

267 


268        ROCK  EXCAVATION— METHODS  AND  COST. 

torn  shear  off  upon  blasting.  The  sides  of  trenches  in  soft 
rocks  can  be  cut  off  clean  when  the  blast  holes  are  properly 
loaded;  but  tough  granites,  traps,  etc.,  leave  jagged  walls, 
generally  involving  excavation  beyond  the  "neat  lines"  spec- 
ified. In  excavating  thin  bedded,  horizontally  stratified 
rocks  the  drill  holes  seldom  need  to  go  much,  if  any,  below 
the  neat  lines;  that  is,  6  ins.  below  the  bottom  of  the  pipe. 
But  in  excavating  thick  bedded  and  tough  limestones  and 
the  like,  it  is  generally  necessary  to  drill  12  ins.  below  the 
bottom  of  the  pipe.  In  tough  granites,  traps,  etc.,  it  is  often 
necessary  to  drill  at  least  18  ins.  below  grade  in  order  to 
leave  no  knobs  or  projections  after  blasting  that  would  re- 
quire breaking  off  with  bull  points  and  sledges.  Obviously 
the  shallower  the  trench  the  greater  is  the  importance  of 
making  due  allowance  for  this  extra  drilling.  If  a  trench 
is  only  3  ft.  deep  and  it  is  necessary  to  drill  I  ft.  below 
grade,  then  33  per  cent,  must  be  added  to  the  cost  of  drill- 
ing to  grade  in  order  to  cover  the  cost  of  the  extra  drilling 
below  grade;  but  if  the  trench  is  10  ft.  deep,  then  only  10 
per  cent,  of  extra  drilling  is  required.  I  have  known  cases 
where  engineers  have  lowered  the  grade  about  6  ins.  after 
a  long  stretch  of  rock  trench  had  been  completed,  and  have 
required  the  contractors  to  do  this  6-in.  skimming  at  the 
regular  price  per  cubic  yard!  As  a  result,  it  has  cost  the 
contractor  several  times  what  he  received  for  the  work.  In 
such  cases  the  engineers  have  generally  been  ignorant  of 
the  actual  cost  of  trench  work ;  for  otherwise  they  doubtless 
would  have  allowed  an  extra  price. 

Charging  the  Holes. — In  tunneling,  the  explosive  is  most 
effective  if  placed  in  a  pocket  at  the  end  of  the  drill  hole. 
In  narrow  trench  work,  on  the  other  hand,  the  explosive 
should  be  distributed  all  along  the  hole,  leaving  only  enough 
length  for  the  least  possible  amount  of  tamping.  To  one 
who  gives  the  matter  thought  the  reason  is  obvious,  yet  I 
have  seen  contractors  actually  "springing"  holes  in  a  hard 
limestone  trench,  and  thus  wasting  much  labor  and  powder. 


COST  OF  TRENCHES  AND  SUBWAYS.  269 

Contractors  often  take  out  deep  trenches  in  several  benches, 
simply  because  they  think  it  necessary  to  place  all  the  charge 
together.  As  a  matter  of  fact  a  trench  25  ft.  deep,  or  as 
deep  as  the  machine  will  drill,  can  be  taken  out  in  one  lift. 
To  do  this  the  explosive  is  separated  into  several  charges 
in  the  hole,  tamping  being  placed  between  the  charges. 
Where  charges  are  separated  in  this  manner  firing  should 
never  be  done  with  a  fuse,  but  always  with  a  battery.  On 
page  204  I  have  described  a  method  of  charging-  alternate 
sticks  of  dynamite  and  wood  plugs,  the  firing  of  the  top 
stick  sending  all  the  others  off.  In  a  city  this  method  could 
probably  not  be  used  with  safety  because  of  the  danger  at- 
tending such  heavy  blasting. 

Use  of  a  Blasting  Mat. — For  preventing  accidents  due  to 
flying  rocks  all  blasts  in  cities  should  be  covered  either  with 
timbers  or  with  a  blasting  mat.  This  should  be  done  to 
avoid  suits  for  damages,  regardless  of  city  ordinances.  A 
blasting  mat  is  readily  made  by  weaving  together  old  hemp 
ropes,  il/2  in  diam.  or  larger.  To  make  such  a  mat,  sup- 
port two  lengths  of  i-in.  gas  pipe  parallel  with  one  another 
and  as  many  feet  apart  as  the  width  of  the  mat  is  to  be. 
Fasten  one  end  of  the  rope  to  one  end  of  the  pipe;  carry  the 
rope  across  and  loop  it  over  the  other  pipe;  bring  it  back 
around  the  first  pipe ;  and  so  on  until  a  sufficient  number 
of  close  parallel  strands  of  the  rope  have  been  laid  to  make 
a  mat  as  long  as  desired.  Starting  with  another  rope,  weave 
it  over  and  under,  like  the  strands  in  a  cane-seated  chair, 
until  a  mat  of  criss-cross  ropes  is  made.  Such  a  mat, 
weighted  down  with  a  few  heavy  timbers,  will  effectually 
prevent  small  fragments  from  flying  at  the  time  of  blast- 
ing. The  mat  and  its  ballast  may  be  hurled  into  the  air  sev- 
eral feet,  upon  blasting ;  but  it  will  serve  its  purpose  by  stop- 
ping the  small  pieces  of  rock  which  are  so  dangerous  even 
where  light  blasts  are  fired.  The  mat  should  be  laid  directly 
upon  the  rock.  Such  a  mat  will  save  a  great  deal  of  labor 
involved  in  laying  a  grillage  of  timbers  over  a  trench.  It 


270        ROCK  EXCAVATION— METHODS  AND  COST. 

will  also  make  it  unnecessary  for  the  blasters  to  stand  far 
from  the  blast  when  firing. 

Cost  of  Drilling  and  Blasting. — Next  to  tunneling  there  is 
no  class  of  rock  excavation  requiring  so  much  drilling  per 
cubic  yard  as  does  trench  excavation.  In  granites,  if  shallow 
holes  are  drilled  by  hand,  the  holes  are  frequently  spaced 
not  more  than  il/2  ft.  apart.  If  in  a  very  narrow  trench  il/> 
ft.  wide  two  holes  are  drilled  in  a  row,  one  on  each  side  of 
the  trench,  and  if  the  rows  are  il/2  ft.  apart,  we  have  two 
holes  drilled  in  a  square  il/2  ft.  on  a  side;  that  is,  for  every 
2*4  cu.  ft.  of  rock  we  must  drill  2  ft.  of  hole,  or  24  ft.  of 
drill  hole  per  cu.  yd.  If  the  cost  of  drilling  is  25  cts.  a  foot, 
we  have  24  X  -25  =  $6  per  cu.  yd.  as  the  cost  of  drilling 
alone.  It  is  seldom,  however,  that  such  narrow  trenching 
is  done.  Trenches  for  small  pipes  are  usually  2^2  to  3  ft. 
wide;  two  holes  are  then  drilled  in  a  row,  and  rows  are 
usually  about  3  ft.  apart.  A  trench  3  ft.  wide  with  two- 
holes  in  a  row,  and  rows  3  ft.  apart,  requires  6  ft.  of  drill- 
ing per  cubic  yard.  With  drilling  costing  50  cts.  per  ft.,  as 
it  often  does  where  hand  drills  are  used  in  granite,  the  cost 
is  then  $3  per  cu.  yd.  for  drilling  alone.  Unless  the  job  is 
too  small  to  pay  for  installing  a  plant,  hand  drilling  should 
never  be  used  in  trench  work,  because  the  drilling  forms 
such  a  very  large  part  of  the  cost. 

In  a  trench  6  ft.  wide  in  hard  trap  rock  three  holes  were 
drilled  in  a  row,  one  close  to  each  side  and  one  in  the  middle, 
and  the  rows  were  3  ft.  apart,  thus  requiring  4^  ft.  of  drill 
hole  per  cu.  yd.  of  excavation.  The  drilling  was  done  with 
steam  drills  at  a  cost  of  30  cts.  per  lin.  ft.,  for  the  holes  were 
only  4^2  ft.  deep,  the  rock  was  hard,  and  the  men  slow, 
about  35  ft.  being  the  day's  work  per  drill.  The  contractor 
had  to  drill  i^  ft.  below  grade  in  this  rock  to  insure  having 
no  projecting  knobs  of  rock.  While  it  cost  $1.35  per  cu. 
yd.  to  drill  the  3^2  ft.  for  which  payment  was  made,  to  this 
must  be  added  nearly  30  per  cent.,  or  $0.40  per  cu.  yd.,  to. 
cover  the  cost  of  drilling  the  extra  I  ft.  for  which  no  pay- 


COST  OF  TRENCHES  AND  SUBWAYS.  271 

ment  was  received,  making  the  total  cost  of  drilling  $1.75 
per  cu.  yd.  of  pay  material.  About  2  Ibs.  of  40  per  cent, 
dynamite  were  charged  in  each  hole,  making  about  2.6  Ibs. 
of  dynamite  per  cu.  yd.  of  pay  material.  The  explosives 
thus  added  another  $0.40  per  cu.  yd.,  making  a  total  of  $2.15 
per  cu.  yd.  for  drilling  and  blasting. 

In  the  same  trap  rock,  where  the  trench  was  8  ft.  wide  and 
12  ft.  deep,  there  were  three  holes  in  a  row  and  rows  were 
4  ft.  apart,  requiring  2.53  ft.  of  hole  per  cu.  yd.  of  pay  exca- 
vation, plus  0.21  ft.  of  hole  per  cu.  yd.  of  pay  material  to 
cover  the  cost  of  drilling  the  last  I  ft.  of  hole  below  the 
''neat  line."  Each  drill  averaged  45  ft.  of  hole  in  10  hrs., 
and  the  cost  was  23  cts.  per  ft.  of  hole ;  hence,  2.74  X  0.23  = 
$0.63  per  cu.  yd.  was  the  cost  of  drilling.  About  4  Ibs.  of 
40  per  cent,  dynamite  was  charged  in  each  hole,  or  i.i  Ibs. 
per  cu.  yd.  of  pay  material,  making  the  total  cost  80  cts.  per 
cu.  yd.  for  drilling  and  blasting.  A  comparison  of  this  cost 
of  80  cts.  with  the  $2.15  above  given  brings  out  strikingly 
the  fact  that  each  problem  of  trench  work  must  be  con- 
sidered in  detail  by  itself. 

In  a  city  where  the  contractor  must  shoot  comparatively 
small  shots  in  order  to  avoid  accidents  to  buildings  and  suit^ 
for  damages  arising  from  "disturbing  the  peace,"  it  is  sel- 
dom possible  to  space  the  holes  more  than  3  or  at  most  4  ft. 
apart.  In  trenching  in  soft  sandstone  in  Newark,  N.  J., 
where  the  trench  was  14  ft.  wide  and  10  ft.  deep,  there  were 
five  holes  in  a  row  (the  distance  between  holes  being  3^ 
ft.)  and  rows  were  4  ft.  apart,  making  2.4  ft.  of  hole  per 
cu.  yd.  Each  hole  was  charged  with  4.12  Ibs.  of  40  per  cent, 
dynamite,  making  practically  i  Ib.  per  cu.  yd.  About  half 
the  dynamite  is  charged  at  the  bottom  of  each  hole,  then 
tamping  is  put  in,  and  the  other  half  is  charged  up  to  about 
2l/2  ft.  below  the  mouth  of  the  hole.  Each  steam  drill  aver- 
aged 90  ft.  of  hole  per  10  hrs.,  making  the  cost  of  drilling 
10  cts.  per  ft.  of  hole,  or  24  cts.  per  cu.  yd.  Including  the 
cost  of  dynamite  and  the  placing  of  timbers  over  each  blast, 


272        ROCK  EXCAVATION— METHODS  AND  COST. 

the  cost  of  drilling  and  blasting  was  40  cts.  per  cu.  yd.  This 
is  probably  as  low  a  cost  for  breaking  rock  in  trenching  as 
can  be  counted  upon  under  favorable  conditions.  In  this 
rock  there  was  no  necessity  of  drilling  below  grade. 

I  am  indebted  to  Mr.  F.  J.  Winslow  for  the  following  data 
on  trench  work  in  Boston,  Mass.  House  sewer  trenches  are 
never  less  than  3  ft.  wide,  and  trenches  for  water  pipe  (16 
ins.  or  less)  are  2l/>  ft.  wide.  The  rock  is  granite,  and  the 
drill  holes  are  usually  3  ft.  apart.  On  small  jobs  hammer 
drills  are  used,  one  man  holding  and  two  striking.  For  a 
hole  10  ft.  deep  the  starting  bit  is  2l/2  ins.  and  the  finishing 
bit  is  1^4  ms-  diam.  A  drilling  gang  of  three  men  aver- 
ages 8  to  10  ft.  of  hole  in  10  hrs.,  although  in  soft  rock  20 
ft.  may  be  drilled  in  10  hrs.  Forceite  containing  75  per  cent, 
nitroglycerin  is  commonly  used,  */2  to  3  sticks  being  charged 
in  a  hole.  Force  account  records  for  granite  trenching 
show  that  the  average  cost  during  the  past  15  years  has 
been  $3.80  per  cu.  yd.,  including  excavating  and  piling  up 
the  rock  alongside  the  trench. 

I  am  indebted  to  the  Harrison  Construction  Co.,  of  New- 
ark, N.  J.,  for  the  following  information:  In  a  sandstone 
trench  about  6  ft.  wide  the  holes  were  spaced  about  3  ft. 
apart,  thus  requiring  4^2  ft.  of  hole  per  cu.  yd.  In  seamy 
rock,  shallow  holes  4  to  6  ft.  deep  were  drilled,  and  from  2 
to  3  sticks  of  50  per  cent,  dynamite  were  charged,  each  stick 
being  1^2  x  8  ins.  This  is  equivalent  to  0.55  Ib.  per  cu.  yd. 
Where  the  rock  was  solid,  the  holes  were  drilled  8  to  10  ft. 
deep  and  the  dynamite  charge  doubled. 

The  cost  of  throwing  rock  out  of  shallow  trenches  or  of 
loading  it  into  buckets  to  be  raised  by  the  engine  of  a  der- 
rick, a  locomotive  crane  or  a  cableway,  is  somewhat  greater 
than  the  cost  of  handling  rock  in  open  cuts.  A  fair  day's 
work  for  one  man  is  6  cu.  yds.  of  rock  loaded,  when  there 
is  little  sledging;  but  the  output  may  be  only  4  cu.  yds. 
where  there  is  a  large  amount  of  sledging  to  be  done. 

If  cableways  or  derricks  are  used  for  hoisting  the  rock, 


COST  OF  TRENCHES  AND  SUBWAYS.  273 

bear  in  mind  that  they  will  be  idle  most  of  the  time,  for  the 
drilling  limits  the  output.  With  a  given  number  of  drills 
to  a  cableway,  estimate  the  number  of  cubic  yards  of  rock 
that  the  drills  will  break  per  day  and  divide  this  yardage  into 
the  daily  cost  of  operating  the  derrick.  Thus,  in  a  trench 
6  ft.  wide,  if  the  holes  are  3  ft.  apart,  each  cubic  yard  of  rock 
requires  4^2  ft.  of  hole,  and  each  drill  will  break  13  1/3  cu. 
yds.  per  day  where  60  ft.  of  hole  is  a  day's  work.  With  four 
drills  per  cableway  the  daily  output  is  4  X  13  1/3  =  53  1/3 
cu.  yds.  The  cableway  would  be  capable  of  handling  sev- 
eral times  this  output  were  it  not  limited  by  the  drilling. 
Notwithstanding  that  all  this  seems  self  evident,  I  have 
known  more  than  one  contractor  to  overlook  the  fact  that 
the  cost  of  handling  rock  from  trenches  is  very  much  great- 
er than  in  open  cuts  where  holes  are  farther  apart  and  where 
a  few  drills  can  keep  a  cableway  busy.  In  my  book  on 
earthwork  I  have  given  in  detail  the  cost  of  operating  a 
cableway  on  trench  work,  and  elsewhere  in  this  book  will 
be  found  the  cost  of  hoisting  with  derricks. 

Cost  of  N.  Y.  Subway  Work.  — Aside  from  some  data  on 
the  cost  of  subway  work  given  in  my  book  on  earthwork, 
nothing,  so  far  as  I  know,  has  ever  appeared  in  print  on  the 
actual  cost  of  subway  excavation.  By  observation  and 
through  the  aid  of  an  assistant  I  have  secured  reliable  data 
relating  to  every  item  of  cost  on  several  typical  sections  of 
the  New  York  Rapid  Transit  Rv.,  including  excavation,  con- 
crete, steel  construction,  etc. ;  and  it  is  astonishing  to  find 
how  high  the  labor  cost  of  the  work  has  been.  The  high 
cost  may  be  attributed  to  several  causes.  In  the  first  place, 
the  contractors  were  compelled  to  employ  union  labor, 
much  of  which  was  inefficient.  In  the  second  place 
the  foremen  on  this  work  were,  as  a  rule,  paid  such 
small  salaries  that  the  best  class  of  foremen  were  not 
kept.  In  the  third  place  excavation  and  other  work  in 
crowded  city  streets  is  obviously  made  difficult;  the  sup- 
porting .of  pipes,  tracks,  etc.,  adding  greatly  to  the  cost  in 
certain  parts  of  the  city.  In  fact,  in  the  lower  part  of  New 


274        ROCK  EXCAVATION— METHODS  AND  COST. 

York,  where  the  material  is  all  sand,  I  have  found  that  50 
cts.  per  cu.  yd.  has  been  expended  in  shoring,  bracing,  etc. 
In  the  fourth  place  the  light  blasts  required  by  city  rules 
leave  the  tough  mica  schist  in  large  chunks  upon  which 
much  labor  must  be  expended  in  gadding  and  sledging;  for 
practically  all  the  rock  was  broken  to  one  or  two-man  size 
so  that  it  could  be  hauled  away  in  dump  wagons. 

The  work  that  I  am  about  to  describe  involved  the  excava- 
tion of  about  125,000  cu.  yds.  of  tough  mica  schist  in  the 
upper  part  of  the  city,  where  the  streets  are  not  crowded 
and  where  there  were  very  few  pipes  to  be  supported.  The 
width  of  the  excavation  was  41  ft.,  and  the  depth  averaged 
about  30  ft.  One  trolley  track  ran  along  the  center  of  the 
street  and  had  to  be  supported  the  entire  distance.  This 
track  supporting  was  accomplished  at  comparatively  slight 
expense  by  using  some  ten  second-hand  railroad  bridge 
trusses  of  66  ft.  span,  which  were  moved  forward  as  the 
work  progressed.  Five  cableways,  each  having  an  average 
span  of  400  ft.,  were  used  for  hoisting  the  rock  in  self- 
righting  buckets,  which  were  dumped  into  patent  dump 
wagons. 

The  average  daily  force  employed  was  as  follows : 

Rate  per  day.  Total. 

4  foremen $3-5°  $14.00 

80  laborers 1.50  120.00 

10  drill  runners 2.75  27.50 

10    "    helpers 1.50  15.00 

2  blacksmiths 2.75  5.50 

2                     helpers  ....  1.50  3.00 

5  hoisters   3.00  15.00 

I  compressor  man 4.00  4.00 

1  fireman   2.00  2.00 

2  timbermen    2.00  4.00 

3  Waterboys 75  2.25 

20  teams 4.50  90.00 


Total  per  8-hr,  day $302.25 


COST  OF  TRENCHES  AND  SUBWAYS. 


275 


The  average  output  of  this  force  was  only  150  cu.  yds.  of 
rock  per  day  ! 

Cost  per  Cu.  Yd. 


Drill  runners    ...........  $2.75  $0.174    ,         $0.150 

Drill  helpers  ............  1.50  .100  .082 

Blacksmiths    .............  2.75  .032  .025 

Blacksmiths'  helpers    ....  1.50  .018  .012 

Compressorman   .........  4.00  .016  .014 

Firemen   ................  2.00  .012  .014 

Hoist  enginemen  ........  3.00  .100  .051 

Carpenters    ..............  3.50  .008  .000 

Timbermen    .............  2.00  .024  .000 

Waterboys    ..............  0.75  .012  .010 

Laborers  ................  1.50  .785  .745 

Foremen    ................  3.50  .102  .095 

Teams  (with  drivers)  ....  4.50  .620  .581 

Total  Wages  .......  $2.002  $  1.779 

Cu.  Yds.  Excavated  125,000  7,600 

To  the  foregoing  must  be  added  the  cost  of  fuel,  explo- 
sives, maintenance,  interest  and  depreciation  of  plant,  etc., 
as  follows: 

Cost  per  cu.  yd. 
Vso  ton  coke,  at  $4.50  .........  ..........  $0.150 

0.6  Ib.  40  p.  c.  dynamite,  at  12^2  cts  .......  °-°75 

y>  exploder,  at  4  cts  .....................  0.020 

Drill  repairs  (est'd  at  50  cts.  a  day  per  drill)     .034 
Installing  boiler  and  compressor  ...........  014 

Interest  and  depreciation  (50  p.  c.)  of  $7,000 
boiler  and  compressor  plant  .............  028 

Ditto  for  $3,500  drilling  plant  .............  014 

Total  supplies,  etc  ...................  $°-335 

Add  total  wages   .......................  2.002 


$2.337 


276        ROCK  EXCAVATION— METHODS  AND  COST. 

To  this  sum  should  be  added  3  or  4  per  cent,  to  cover  gen- 
eral expenses,  such  as  office  rent,  bookkeeping,  night  watch- 
men, insurance  on  laborers,  etc.,  which  would  bring  the 
grand  total  to  nearly  $2.40  per  cu.  yd.  of  rock  excavated. 
It  will  be  seen  by  the  description  of  the  work  and  by  the 
comparatively  low  cost  of  timberwork  that  the  expense  of 
supporting  pipes  and  tracks  was  unusually  low  for  such  a 
city  as  New  York.  On  the  other  hand,  the  cost  of  drilling 
was  exceedingly  high,  being  28  cts.  per  cu.  yd.  for  wages 
alone,  if  we  include  the  blacksmiths'  wages  and  half  the 
wages  of  the  compressorman  and  his  fireman.  The  drills 
should  be  charged  with  about  half  the  cost  of  the  fuel,  which 
adds  Jl/2  cts.  more  per  cu.  yd.,  making  35^  cts.  per  cu.  yd. 
for  drilling,  not  including  some  3^  cts.  for  drill  repairs 
(estimated)  and  il/>  cts.  for  interest  and  depreciation.  Add- 
ing these  two  items  we  have  a  total  of  40  cts.  per  cu.  yd. 
chargeable  to  drilling  alone,  which  is  exceedingly  high  for 
an  open  cut  of  this  width  and  depth.  It  is  a  striking  fact 
that  each  drill  broke  less  than  15  cu.  yds.  of  rock  per  8-hr, 
day.  The  inefficiency  of  the  laborers  is  also  well  shown  by 
their  output  of  less  than  2  cu.  yds.  per  man  per  8-hr.  day. 
It  is  true  that  they  had  to  do  a  great  deal  of  gadding,  sledg- 
ing and  hand  drilling  to  break  the  rock  ready  to  load  into 
buckets ;  but  any  one  who  saw  the  men  at  work  must  have 
been  impressed  with  their  slowness.  The  output  of  only  30 
cu.  yds.  per  day  per  cableway  shows  how  the  cableway  out- 
put was  limited  by  the  drilling.  The  high  cost  of  hauling  is 
also  noteworthy,  for  the  average  haul  was  but  little  more 
than  one  mile. 

While  it  was  difficult  to  get  union  laborers  to  do  a  fair 
day's  work,  I  think  that  if  the  contractors  along  the  subway 
had  in  all  cases  employed  civil  or  mining  engineers  of  known 
experience  in  rock  excavation,  a  great  deal  of  money  would 
have  been  saved. 


CHAPTER  XV. 

SUBAQUEOUS   EXCAVATION. 

Cost  of  Rock  Excavation  in  the  Detroit  River. — I  am  in- 
debted to  Mr.  Chas.  Y.  Dixon,  U.  S.  Assistant  Engineer,  for 
the  following  data  of  cost,  which  were  originally  compiled  by 
Mr.  Harry  Hodgman,  and  which,  so  far  as  I  know,  are  the 
most  detailed  and  complete  cost  records  of  subaqueous  ex- 
cavation that  have  ever  been  published.  In  the  Michigan 
Engineer,  1903,  Mr.  Hodgman  gave  a  very  complete  descrip- 
tion of  this  work  upon  which  he  has  been  continuously  en- 
gaged since  1895.  From  Mr.  Hodgman's  article  and  from 
Mr.  Dixon's  letters  to  me,  I  have  compiled  the  following: 
The  work  was  done  under  three  contracts,  as  follows:  At 
Ballards  Reef,  the  Buffalo  Dredging  Co. ;  at  Lime  Kiln 
Crossing,  James  B.  Donnelly,  of  Buffalo,  N.  Y. ;  and  at 
Amherstsburg  Reach,  M.  Sullivan,  of  Detroit,  Mich. : 

At  the  mouth  of  the  Detroit  River  it  is  usually  necessary 
to  drill  and  blast  the  material  before  it  may  be  excavated. 
The  drill  boats  in  use  are  from  60  to  80  ft.  long  and  from  25 
to  30  ft.  wide,  and  are  held  in  position  by  four  spuds,  one  at 
each  corner.  They  are  equipped  with  two  or  more  Inger- 
soll  steam  drills  supported  on  vertical  frames  having  trucks 
to  permit  of  the  drills  being  moved  horizontally  along  the 
edge  of  the  boat.  The  drills  are  raised  and  lowered  during 
the  operation  of  drilling  by  hydraulic  lifts.  The  boiler  fur- 
nishes the  steam  for  operating  the  drills,  the  pumps  used 
in  connection  with  the  hydraulic  lifts,  the  forge,  the  electric 
light  plant  and  other  machinery  with  which  the  ordinary  drill 

277 


278        ROCK  EXCAVATION— METHODS  AND  COST. 

boat  is  equipped.  The  drill  boat  usually  serves  the  purpose 
of  a  machine  shop  where  repairs  are  made  to  the  entire 
dredging  plant.  It  is  always  conveniently  near  to  all  parts 
of  the  work,  and  ordinary  repairs  are  quickly  made,  the  con- 
tractor usually  providing  a  great  variety  of  tools  and  ma- 
chinery for  use  in  cases  of  emergency. 

The  drill  boats  are  usually  operated  day  and  night.  The 
holes  (about  2*/2  ins.  in  diam.)  are  made  at  the  corners  of 
5-ft.  squares  to  a  depth  of  about  3  ft.  below  the  required 
depth,  at  the  rate  of  about  5  ft.  per  hour  per  drill.  The 
amount  of  explosive  used  is  about  one  pound  of  60  per  cent, 
dynamite  per  linear  foot  of  drill  hole.  The  holes  are  charged 
by  inserting  the  sticks  of  dynamite  with  the  exploder  and 
battery  wires  attached  into  the  bottom  of  a  long  pipe,  the 
battery  wires  leading  out  through  a  slit  in  the  side  of  the 
pipe.  This  pipe  is  lowered  into  the  drilled  hole,  the  dyna- 
mite shoved  down  with  a  long  ram  rod,  and  the  pipe  with- 
drawn, a  wire  spring  clamped  to  the  dynamite  stick  pre- 
venting its  coming  out  of  the  hole.  The  wires  are  then  at- 
tached to  the  battery  and  the  dynamite  exploded.  During 
this  operation  the  drill  boat  is  not  moved,  nor  does  the  work 
of  operating  the  other  drills  cease  except  at  the  time  of  firing. 
On  two  occasions,  however,  the  charge  of  dynamite  came 
out  of  the  hole,  and  was  exploded  directly  underneath  the 
boat,  causing  it  to  sink  almost  immediately.  This  may  be 
attributed  to  carelessness,  however,  as  before  exploding  the 
dynamite  the  battery  wires  should  be  drawn  up  until  taut, 
indicating  that  it  is  in  place.  A  quantity  of  dynamite  is  al- 
ways kept  conveniently  near  the  work,  but  no  more  than 
one  day's  supply  is  kept  at  the  drill  boat,  and  this  is  stored 
in  a  small  scow  trailing  off  the  down-stream  end  of  the  boat 
at  a  safe  distance. 

The  dredges  used  in  excavating  the  material  are  of  the 
type  known  as  the  dipper  dredge.  They  vary  in  length  from 
80  to  135  ft.  and  in  width  from  30  to  40  ft.,  and  are  held  in 
position  by  three  spuds  (36  ins,  square),  two  at  the  bow  and 


SUBAQUEOUS  EXCAVATION.  279 

one  at  the  stern.  The  machinery  for  operating  dredges  varies 
greatly,  the  best  recently-constructed  dredges  being  equipped 
with  machinery  for  raising  the  dredge  on  the  forward  spuds 
(known  as  pinning  up)  instead  of  by  swinging  the  dipper 
as  formerly.  The  dredge  is  moved  forward  in  the  cut  by 
means  of  the  dipper  arm,  and  the  width  of  the  cut  is  usually 
from  15  to  20  ft.  The  capacity  of  the  dredge  dipper  varies 
from  2  to  5  cu.  yds.  in  rock  work  and  from  4  to  7  cu.  yds. 
for  earth  work.  The  amount  of  material  removed  by  one 
dredge  per  hour  varies  from  20  to  100  cu.  yds.  in  rock,  and 
from  75  to  125  cu.  yds.  in  earth.  The  best  type  of  dredges, 
however,  in  soft  earth  and  under  favorable  conditions  are 
capable  of  removing  from  250  to  300  cu.  yds.  per  hour.  The 
time  delayed  for  repairs  usually  varies  from  one-fifth  to  one- 
third  of  the  time  actually  worked. 

After  the  entire  width  of  the  area  to  be  improved  has  been 
worked  over  by  the  dredge,  cut  by  cut,  the  derrick  scow  fol- 
lows after  to  remove  such  loose  pieces  of  rock  as  may  have 
been  left  projecting  above  the  required  depth.  The  derrick 
scows  are  usually  from  80  to  100  ft.  long  and  from  20  to  25 
ft.  wide  and  they  are  equipped  with  an  ordinary  hoisting 
engine  and  derrick  capable  of  lifting  from  12  to  18  tons,  and 
a  complete  diving  outfit.  When  lifting  the  boulders,  the 
derrick  scow  is  pinned  up  and  supported  on  two  spuds,  each 
about  i  ft.  square.  The  material  to  be  removed  is  found  by 
means  of  an  iron  bar,  about  30  ft.  long,  suspended  from  the 
side  of  the-  scow  to  the  required  depth.  Any  obstruction 
struck  by  this  bar  as  the  scow  is  swept  over  the  improved 
area  is  removed  by  the  derrick  by  means  of  a  chain,  which  is 
placed  in  position  by  a  diver. 

After  the  area  has  been  thus  improved  and  cleared  of  ob- 
structions an  examination  is  made  on  the  part  of  the  United 
States  to  determine  if  the  required  depth  has  been  secured. 
This  examination  consists  in  sweeping  the  entire  area  with 
bars  suspended  to  the  required  depth.  These  bars  (about 
20  ft.  long)  are  suspended  by  chains  from  a  raft  (100  ft 


280        ROCK  EXCAVATION— METHODS  AND  COST. 

long  and  20  ft.  wide)  built  of  squared  timbers,  the  raft  being 
held  in  position  by  a  rope  leading  to  a  head  anchor  and  pulled 
back  and  forth  by  means  of  ropes  leading  to  side  anchors. 
Any  obstruction  found  during  this  examination  is  removed 
by  the  derrick  scow  with  diving  outfit.  During  the  progress 
of  the  work,  as  well  as  during  this  final  examination,  con- 
stant attention  is  paid  to  the  water  gage  in  order  to  allow 
for  the  fluctuations  in  the  water  surface.  Following  this 
examination  and  on  the  completion  of  the  work  required  un- 
der the  contract,  the  final  survey  is  made,  which  survey  con- 
sists in  the  taking  of  soundings  at  regular  intervals  as  de- 
scribed above.  On  this  final  survey  and  on  the  original  sur- 
vey depend  the  estimate  for  final  payment. 

At  Ballard's  Reef  the  material  excavated  was  limestone 
bedrock,  clay,  hardpan  and  boulders.  Generally  there  was 
from  one  to  two  feet  of  loose  material  overlying  the  bed- 
rock. About  50  per  cent,  of  the  material  was  hardpan  and 
clay.  The  material  within  about  75  per  cent,  of  the  area  im- 
proved required  to  be  drilled  and  blasted  before  removal.  In 
this  material  one  drill  boat,  equipped  with  three  drills  and 
working  double  shifts,  was  used  to  provide  work  for  one 
dredge. 

At  Lime  Kiln  Crossing  the  material  was  mainly  limestone 
bedrock,  with  no  overlying  material.  Within  the  entire  area 
it  was  necessary  to  do  drilling  and  blasting  before  dredging. 
In  this  material  two  drill  boats  (each  equipped  with  three 
drills  and  working  double  shifts)  were  used  to  provide  work 
for  one  dredge. 

At  Amherstburg  Reach  the  material  was  limestone  bed- 
rock, clay  and  boulders.  Generally  there  was  from  one  to 
two  feet  of  loose  material  overlying  the  bedrock.  Within 
about  75  per  cent,  of  this  area  it  was  necessary  to  do  drilling 
and  blasting  before  dredging.  On  this  work  two  drill  boats 
(each  equipped  with  three  drills  and  working  double  shifts) 
were  used  to  provide  work  for  two  dredges  continuously  and 
for  a  part  of  one  season  three  dredges, 


SUBAQUEOUS  EXCAVATION. 

TABLE  XXXIV. 
DREDGING  DETROIT  RIVER,  1900-1903. 


281 


Cu.  yds.  above  23  ft.  depth  (place  measure)  74,143  101,072  98,332 

Cu.  yds.,  total  (place  measure) 135,548  121,707  209,821 

Cu.  yds.,  total  (scow  measure) !53,O97  168,633  

Area  dredged,  sq.  yds 225,000  61,000  225,000 

Average  depth  dredged,  pay  material....  i  ft.  5  ft.  1.3  ft. 

Average  depth  dredged,  total  exc 1.8  ft.  6  ft.  2.8  ft. 

Average  depth  of  water  over  material 21  ft.  18  ft.  20.7  ft. 

Dredge  hours,  worked 7,248  3,945  9,021 

Dredge  hours,  delayed 3,386  1,490  2,890 

Dredge  hours,  total 10,634  5,435  12,91 1 

Dredge  months  (i2-hr.  days) 34  17.4  39 

Cost  per  month $3,ooo  $3,200  $3,200 

'i  otal  cost $102,000  $55,720  $124,800 

Cost  per  cu.  yd.  (place  measure),  pay 

material  $1.38  $0.55  $1.27 

Cost  per  cu.  yd.  (place  measure),  total 

exc $0.75  $0.46  $0.60 

Average  cu.  yds.  per  hr.,  working  time. .. .  19.0  43.0  23.3 

Average  cu.  yds.  per  hr.,  total  time 12.8  22.4  16.2 

iViaximum  cu.  yds.  per  hr.,  soft  material..  150  250  200 

TABLE  XXXV. 
DRILLING. 


Worked 

Drill   hours     -I  Delayed 

Total 

Number  of  holes  drilled 

Number  of  feet   drilled 

Ft.  per  hr.,  actual   work 

Ft.  per  cu.  yd.,  pay  material.. 

Ft.  per  cu.  yd.,  total  exc 

Distance   between   holes 


Ballards    Lime  Kiln 

Reef.      Crossing. 

24,442 

982 

25,424 

30,023 

191,850 

7-9 
2.6 


1.4 
ft. 


37,746 
1,278 
39,024 
29,236 
240,591 

6-4 
2.4 
1.9 
5     ft- 


Amherstburg 
Reach. 
38,441 


38,441 

35,432 

181,421 

4-7 

1.8 

0.9 

5     ft 


282        ROCK  EXCAVATION— METHODS  AND  COST. 

Average  depth  of  holes 6.2  ft.  8.2  ft.  5.1  ft. 

Average  depth  of  pay  material  i.o  ft.  5.0  ft.  1.3  ft. 
Percentage  of  drilling  below 

pay  depth  84.0%  37-5%  75-O% 

Number  of  pounds  of  60% 

dynamite  110,305  222,396  263,672 

Lbs.  per  cu.  yd.,  pay  material.  0.5  2.2  2.7 

Lbs.  per  cu.  yd.,  total  exc....  0.8  1.8  1.2 

iotal  cost  of  drilling $59,235  $105,245  $96,470 

Per  cu.  yd.,  pay  material $0.80  $1.04  $0.98 

Per  cu.  yd.,  total  exc $0.44  $0.865  $0.46 

Per.  lin.  ft.  drilled $0.31  $0.44  $0.53 

Per  drill  hour $2.25  $2.69  $2.51 

ITEMS  OF  COST. 

Ballards   Reef.  Lime   Kiln   Crossing. 

25,424     drill     hours     at  39,024     drill     hours      at 

$0.80    $20,340  $0.80    $31,220 

IT0,305   Ibs.    dynamite   at  222,400   Ibs.    dynamite   at 

$0.15    i6,545  $0.15    33,36o 

2,450    tons    of    coal     at  3,555     tons    of    coal     at 

$3-00   7,350  $3.00   10,665 

Repairs    (approximate)..       5,ooo  Repairs    (approximate).       5,ooo 

Miscellaneous  supplies    .       5,ooo  Miscellaneous  supplies   .       5,ooo 

Depreciation  of  plant...       5,OOD  Depreciation  of  plant...       5,ooo 

Tug  service,  30  mos.   at 

Total    $59,235  $500   15,000 

Tug  service  included  in  dredg- 
ing. Total $105,245 

Amherstburg  Reach — 

38,441  drill  hours  at  80  cts $30,750 

263,372  Ibs.  dynamite  at  15  cts 39»5OO 

3,740  tons  of  coal  at  $3 1 1,220 

Repairs  (approximate)   5,ooo 

Miscellaneous  supplies  (approximate) 5,000 

Depreciation  of  plant  (approximate) 5,ooo 


Total 

Tug  service  included  in  dredging. 


,$96,470 


Cost 


SUBAQUEOUS  EXCAVATION. 
TABLE   XXXVI. 

DERRICK   Scows. 


283 


Ballards 

Lime   Kiln 

Amherstburg 

Reef. 

Crossing. 

Reach. 

at  $970 

13.0  mos. 

16.0  mos. 

1  1.2  mos. 

at  $970 

at  $970 

$10,865 

$12,610 

$15,520 

Tug  service 

Tug  service 

Tug  service 

included   in 

included    in 

included   in 

dredging. 

dredging. 

dredging. 

of 


area 


Cost    per    sq.    yd. 

improved    

Cost,  per  cu.  yd.  of  material 

removed  by  diver 


$0.0475 
$573 


$0.22 
$2.84 


$0.07 
$2.04 


SUMMARY  OF  COST. 


Dredging 

Drilling    

Derrick  scows 


$102,000 

59,235 
10,865 


$55720 

105,245 

12,610 


$124,800 
96,470 
15,520 


Totals $172,100         $173,575          $236,790 

Cost    per    cu.     yd.     of    pay 

material    $2.32  $1.718  $2.41 

Cost    per    cu.    yd.    of    total 

excavation    $1.27  $1425  $1.04 

BASIS  UPON  WHICH  ESTIMATES  OF  COST  WERE  MADE. 


Dredge  Crew : 


Captain  at  $125  per  month $125 

Runner  at  $90  per  month 90 

Cranesman   at   $90   per   month 90 

Fireman    at   $55    per   month 55 

Deckhands  at  $40  per  month 120 

Scowman   at   $40   per   month 40 

Cook  at  $50  per  month 50 

Watchman  at  $40  per  month 40 


Total    $610 


284        ROCK  EXCAVATION—  METHODS  AND  COST. 

Tug  Crew  :     i  Captain    at    $115    per    month  ..............  $H5 

i   Engineman   at   $100   per   month  ............  100 

i  Fireman  at  $55  per  month  .................  55 

i  Deckhand    at   $40   per   month  ..............  40 

Total     ..................................  $310 


Subsistence  of  14  men  per  month 

210  tons   of  coal   at  $3  ......................     630 

Repairs    and    supplies    per    month  ............     500 

Repairs    at    the    end    of    season,    per    working 

month    .................................     500 

Depreciation  in  value  of  plant  per  month  of 

operation   equals   Y%   of   10%   of  value  of 

plant. 

DRILLING 

3J/2  men  per  drill  (at  $2.50  per  day  of  11  hours)  equals 
80  cts.  per  drill  per  hour. 

DERRICK   SCOW 

I  foreman  at  $90  per  month  ................  $90 

I  -engineman  at  $85  per  month  ..............  85 

i  diver,  25  days,  at  $10  per  day  ............  250 

i  diver's  helper,  at  $75  per  month  ...........  75 

6  deck-hands,  at  $50  per  month  .............  300 

15  tons  of  coal  at  $3  .......................  45 

Repairs  and  supplies  per  month  ............  50 

Depreciation  in  value  of  plant  .............  75 


Cost  per  month $970 

Cost  of  Harbor  Excavation,  Oswego,  N.  Y. — In  Engineering 
News,  Feb.  15,  1894,  Mr.  Wm.  Pierson  Judson  gives  the 
following  data  on  rock  excavation  in  the  inner  harbor  of 
Oswego.  N,  Y.  Over  an  area  of  4,500  sq.  yds.  the  rock  had 
to  be  excavated  to  a  depth  of  15  ft.  Over  70  per  cent,  of 
this  area  the  rock  had  a  face  of  i  ft.  or  less,  and  over  the 
rest  the  face  was  2  ft.  or  less.  The  rock  was  gray  wacke 
sandstone  in  horizontal  strata  i  to  2  ft.  thick,  with  seams  in 
which  the  drill  often  jammed.  The  rock  varied  greatly  in 


SUBAQUEOUS  EXCAVATION.  285 

hardness ;  the  drill  often  cutting  10  ft.  with  one  sharpening, 
and  at  other  times  wearing  dull  in  I  ft.  The  rock  excavated 
was  2,956  cu.  yds.,  let  to  Kingston,  Rogers  &  O'Brien  at 
$2.75  per  cu.  yd.,  place  measure.  Work  was  begun  June 
30,  1893,  with  a  very  efficient  plant. 

The  drill  scow  was  6l/2  x  26  x  82  ft.,  the  bottom  being 
of  8-in.  oak,  and  the  sides  of  6-in.  pine,  and  after  a  season's 
work  showed  no  ill  effects  from  blasts  fired  directly  under 
it  in  12  ft.  of  water.  Its  draft  was  2l/2  ft.  A  deck  house  14 
x  72  ft.  housed  boiler,  engine  and  blacksmith  shop.  On 
one  side  of  this  house  was  a  6l/2-ii.  track  carrying  two  drill 
frames  each,  one  a  separate  truck  that  could  be  moved  by 
two  men  operating  a  5-ft.  lever  and  ratchet  engaging  a  10- 
in.  pinion  on  the  truck  shaft.  Each  drill  frame  carried  a 
5-in.  Ingersoll  drill,  suspended  from  a  6-in.  x  12-ft.  hydrau- 
lic lift  set  vertically  in  the  drill  frame.  The  great  value  of 
this  hydraulic  hoist  was  that  it  could  pull  a  drill  loose  in- 
stantly when  stuck  in  a  seam.  These  hydraulic  hoists  were 
operated  by  a  duplex  Blake  pump  with  a  7^2-in.  steam  cyl- 
inder, 4^2-in.  water  cylinder  and  lo-in.  stroke,  working  un- 
der 80  Ibs.  steam  pressure.  Steam  for  the  drills,  pump  and 
I5-H.  P.  hoisting  engine  was  supplied  by  a  3O-H.  P.  boiler 
burning  1^2  tons  of  coal  in  a  working  day  of  22  hrs.  There 
were  two  crews  of  six  men  each,  and  a  blacksmith  and  help- 
er with  each  crew. 

Range  marks  10  ft.  apart  made  it  possible  to  locate  a  drill 
within  i  ft.  of  any  desired  spot.  A  4^2-in.  casing  pipe  was 
lowered  and  forced  into  the  gravel  overlying  the  rock.  This 
pipe  had  a  double  T,  2  ft.  above  the  bottom,  to  allow  drill 
chips  to  escape.  The  pipe  remained  in  position  until  the 
hole  was  drilled  and  charged.  The  drill  steel  is  26  ft.  long, 
the  upper  14  ft.  being  of  i^-in.  machine  steel ;  the  next  10  ft. 
of  i^-'m.  steel,  and  the  lower  2  ft.  of  2-in.  octagon  steel  with 
a  3/4"m-  square  cross  bit  tempered  in  a  saturated  solution 
of  equal  parts  of  sal  ammoniac,  salt  and  alum. 

Holes  were  drilled  2  to  4  ft.  below  grade,  and  spaced  5  ft. 


286        ROCK  EXCAVATION— METHODS  AND  COST. 

apart  in  rows  5  ft.  apart.  The  average  depth  of  1,000  holes 
was  5*4  ft.  and  the  average  time  to  drill  each  of  these  holes 
was  i  hr.,  although  in  rock  free  from  seams  a  hole  may  be 
drilled  in  l/2  hr.,  whereas  in  seamy  rock  3  hrs.  may  be  con- 
sumed. The  maximum  rate  of  penetration  of  the  drill  was 
I  ft.  in  4  mins.  About  12  drills  per  22  hrs.  were  sharpened. 
About  20  ft.,  or  240  Ibs.,  of  2-in.  octagon  steel  for  6,000  ft. 
of  holes. 

Dynamite  (75  per  cent.)   in  waterproof  cases,  2T/2  x  18 
ins.,  gave  the  best  results.     The  cartridge  is  placed  in  an 
iron  loading  pipe,  which  hangs  by  a  small  tackle  from  the 
drill  frame.     When  the  bottom  of  the  hole  is  reached,  a 
plunger,  which  is  within  the  loading  pipe,  is  undamped  and 
forced  steadily  down  upon  the  cartridge,  while  the  loading 
pipe  is  slowly  hoisted.     The  plunger  and  loading  pipe  are 
next  raised  through  the  casing;  then  the  casing  pipe  itself 
is  raised  4  or  5  ft.  from  the  bottom ;  and  in  this  position  the 
charge  is  fired,  one  hole  at  a  time,  without  moving  the  drill 
boat.     From  2  to  6  Ibs.,  average  234  Ibs.,  of  dynamite  are 
fired  in  each  hole.     The  entire  time  from  the  stopping  of 
the  drill  to  the  firing,  as  just  described,  is  3  mins.  in  ordinary 
work,  and  often  only  il/2  mins.     To  shift  the  drill  on  its 
trucks  5  ft.  lower  the  casing  and  start  drilling  a  new  hole 
takes  about  2  mins.  and  can  be  done  in   I  min.     Fourteen 
holes  5  ft.  apart  can  be  fired  from  one  setting  of  the  drill 
boat.     The  rock  is  broken  up  into  pieces  of  i  to  2  cu.  ft. 
each.    Occasionally  the  dredge  dipper  brings  up  a  rock  too 
large  to  drop  through  the  dipper.     In  such  cases  the  dipper 
is  rested  on  the  dump  scow,  while  a  hole  is  drilled  in  the 
rock  with  a  hand  drill,  loaded  with   l/2    Ib.    of    dynamite, 
tamped  with  cotton  waste  and  fired  without  injury  to  the 
dipper. 

The  loading  pipe,  above  mentioned,  is  worthy  of  descrip- 
tion. Its  lower  end  is  a  2^-in.  pipe  3  ft.  long,  with  a  ^g-in. 
slot  its  full  length.  The  upper  end  of  this  slotted  pipe  joins 
a  i-in.  pipe  22  ft.  long,  within  which  works  a  ^-in.  plunger 


SUBAQUEOUS  EXCAVATION.  287 

27  ft.  long,  having  a  2-in.  head  at  its  lower  end  resting  on 
the  cartridge.  The  leading  wires  from  the  cartridge  pass 
out  through  the  slot.  A  clamp  at  the  upper  end  of  the  i-in. 
pipe  holds  the  plunger  until  ready  to  use.  The  device  is  all 
of  iron  and  works  perfectly.  While  the  exact  cost  to  the 
contractors  is  not  known,  the  following  estimate  is  based 
upon  1,000  cu.  yds.  of  rock,  for  which  1,650  holes,  aggre- 
gating 8,660  lin.  ft.,  were  drilled  in  33  days  of  22  hrs.  each : 

33  days'  wages  of  drill  crew,  at  $31 $1,023.00 

4,000  Ibs.  of  75  p.  c.  dynamite,  at  17  cts..      680.00 

1,800  exploders  at  3  cts 54.00 

49^  net  tons  of  soft  coal,  at  $3 148.50  • 

42  1/3  gals,  cylinder  oil  for  drills,  etc.,  at 

30  cts 12.70 

55  gals,  kerosene  for  lanterns,  at  12  cts.  .  .          6.60 

260  Ibs.  octagon  steel,  at  15  cts 39«oo 

55  Ibs.  machine  steel,  at  4  cts 2.20 

General  machine  shop  repair  bill 34«oo 


Total,  1,000  cu.  yds.  ,at  $2 $2,000.00 

To  dredge  1,000  cu.  yds.  required  about  10  days'  work 
of  10  hrs.  each,  costing,  say,  $500,  making  a  total  cost  of 
$2.50  per  cu.  yd.  of  rock  excavation,  not  including  plant 
rental.  While  1,000  cu.  yds.  were  removed  above  grade, 
for  which  the  contractor  was  paid,  there  was  probably  an 
equal  amount  of  loose  rock  left  below  grade,  for  which,  of 
course,  no  payment  was  made. 

Cost  of  Excavating  Black  Tom  Reef,  N.  Y. — In  Farrow's 
Military  Encyclopedia  are  given  some  valuable  data  on  sub- 
marine rock  excavation,  from  which  I  have  abstracted  the 
following  relating  to  the  excavation  o'f  Black  Tom  Reef  in 
New  York  Harbor.  Mr.  W.  L.  Saunders  was  in  charge  of 
this  work  and  designed  apparatus  which  marked  an  epoch 
in  submarine  drilling  and  blasting.  The  work  was  begun 
May  2,  1 88 1,  and  was  completed  in  344  actual  working  days 
{35  days  were  lost  by  storms  and  26  in  equipping  scow). 


288        ROCK  EXCAVATION— METHODS  AND  COST. 

The  drilling  plant  consisted  of  three  5-in.  Ingersoll  drills 
mounted  on  a  platform  supported  by  spuds  ;  a  scow  anchored 
alongside  carried  the  boiler  that  furnished  steam  to  the 
drills.  The  longest  drill  steel  used  was  28  ft.  long,  and  the 
shortest,  16  ft. ;  the  starting  bit  was  3^4  ins. ;  the  finishing 
bit,  2^2  ins.;  and  9  ft.  of  hole  were  drilled  on  an  average 
with  each  bit  before  sharpening.  The  drilling  shift  was  10 
hrs.  long,  one  shift  a  day;  and  20.8  ft.  of  hole  per  drill  per 
shift  was  the  average  drilled  in  the  mica  schist,  not  includ- 
ing the  penetration  of  some  6  ft.  of  sand  and  gravel  over- 
lying the  rock.  Mr.  Saunders  invented  an  "ejector"  which 
is  a  pipe  surrounding  the  drill  steel  and  through  which  water 
is  forced  to  wash  away  the  gravel  and  sand.  1,736  holes 
were  drilled,  1,629  charged  and  1,542  blasted;  the  average 
depth  in  rock  being  10.17  ft.  The  distance  between  holes 
was  4  ft.;  the  area  excavated,  32,100  sq.  ft.,  and  the  rock 
removed,  5,136  cu.  yds.,  place  measure.  The  dynamite  was 
75  per  cent.,  of  which  20,461  Ibs.  were  used ;  exploders, 
1,844;  drill  steel,  395  Ibs. ;  connecting  wire,  77  Ibs. ;  coal,  200 
tons  at  $4.14;  hose,  $491 ;  water,  $500.  For  each  cubic  yard 
3.44  ft.  of  hole  were  drilled,  and  3.98  Ibs.  of  dynamite  used. 
The  cost  of  the  plant  was : 

Barge  and  equipment $6,640 

Two  drill  floats  9,082 

Alterations,  machinery,  etc 5*663 


Total    $21,385 

The  cost  of  drilling  and  blasting  was : 

Cost  per  cu.  yd. 

3.98  Ibs.  75  p.  c.  dynamite $1.84 

1.22  oz.  steel 02 

Coal  and  water 25 

Labor  (payroll,  $26.76  per  day)   1.79 

Repairs,  plant 31 

drills 01 

ejector  pipes 05 


SUBAQUEOUS  EXCAVATION.  289 

Repairs,  hose   $0.09 

Wire  and  tape    Ol 

Total $4-37 

To  this  must  be  added  the  $1.95  per  cu.  yd.  paid  for 
dredging  by  contract. 

Cost  of  Undermining  Flood  Rock. — This  work  is  described 
in  detail  in  Farrow's  Military  Encyclopedia,  and  while  the 
method  of  undermining  is  not  likely  to  be  used  again  for 
harbor  deepening,  there  are  certain  features  that  merit  at- 
tention. Flood  Rock  was  a  Q-acre  obstruction  in  New  York 
Harbor,  and  under  the  direction  of  Gen.  John  Newton  it  was 
finally  removed  in  1885.  Two  shafts  were  sunk  and  10  x  10- 
ft.  drifts  or  galleries  were  run  at  right  angles  to  one  an- 
other, leaving  pillars  of  rock  15  ft.  square  supporting  a  rock 
roof  averaging  19  ft.  thick,  although  in  places  it  was  only 
10  ft.  thick.  In  driving  the  drifts  very  small  charges  of 
rackarock  were  fired,  one  hole  at  a  time,  to  insure  safety 
from  flooding  through  unexpected  seams  in  the  mica  schist 
rock.  Any  seams  encountered  were  plugged  with  cement. 
In  driving  the  10  x  lo-ft.  drifts,  6  Ibs.  of  rackarock  and  12 
ft.  of  drill  hole  were  required  per  cubic  yard.  The  total 
drifting  was  21,669  ft-»  or  80,232  cu.  yds.,  requiring  480,000 
Ibs.  of  explosive.  The  pillars  and  roof  (270,717  cu.  yds.; 
were  drilled  and  charged  with  1.04  Ibs.  of  explosive  per  cu. 
yd.  of  rock,  requiring  0.42  ft.  of  drill  holes  per  cubic  yard. 
The  final  charge  in  the  pillars  and  roof  was  240,400  Ibs.  of 
rackarock  and  43,300  Ibs.  of  No.  i  dynamite,  in  11,789  drill 
holes  in  the  roof  and  772  drill  holes  in  the  pillars,  or  a  total 
of  113,120  ft.  of  drill  holes.  The  cost  of  the  work  and  ex- 
plosives required  in  preparing  for  the  final  blast  was  $2.69 
per  cu.  yd.  of  total  excavation ;  and  the  rackarock  used  in  the 
final  blast  cost  $106,510.  The  loading  of  the  final  charge 
(283,730  Ibs.)  of  explosives  was  done  by  20  men  working  8 
to  12  hrs.  a  day  for  70  days.  Experiments  had  shown  that 
a  lo-lb.  charge  of  No.  I  dynamite  under  water  would  ex- 


290        ROCK  EXCAVATION— METHODS  AND  COST. 

plode  another  charge  in  a  copper  cartridge  27  ft.  away,  so 
that  no  electric  connecting  wires  were  needed  between  drill 
holes.  The  rackarock  was  loaded  in  thin  (.005  in.)  copper 
cartridges,  which  were  soldered  with  a  solder  that  was  melt- 
ed with  wet  steam.  The  main  charge  in  each  hole  was  rack- 
arock, but  the  last  cartridge  in  each  hole  was  No.  I  dyna- 
mite, which  was  allowed  to  project  6  ins.  outside  of  the  hole. 
Every  25  ft.  apart  along  the  drifts  were  placed  cartridges 
(zy2  x  24  ins.)  of  No.  I  dynamite  packed  solid  in  a  thin 
copper  shell ;  and  directly  above  each  of  these  cartridges  was 
a  rigid  brass  cartridge  (2x8  ins.)  containing  No.  I  dyna- 
mite packed  loosely  and  an  electric  exploder.  The  mine  was 
flooded  with  water  and  fired.  There  was  no  loud  report  and 
the  concussion  was  comparatively  slight. 

A  contract  was  let  for  dredging  the  rock  at  $3.19  per  cu. 
yd. ;  but  pending  the  award  of  the  contract  a  derrick  scow 
was  used  and  removed  15  to  30  tons  daily  at  a  cost  slightly 
less  than  the  subsequent  contract  price.  Large  blocks  were 
chained  by  divers.  Later  the  contractors  raised  120  tons 
a  day,  using  two  large  grapple  dredges.  It  is  apparent  from 
these  meagre  data  that  the  rock  was  broken  in  large  chunks 
which  were  dredged  with  great  difficulty. 

The  Derby  Tubular  Drill  Bit.— Lieut.  Geo.  McC.  Derby 
(now  Major  of  Engineers,  U.  S.  A.)  invented  a  drill  bit 
that  was  used  in  drilling  on  the  Flood  Rock  work,  and  it 
proved  so  greatly  superior  to  the  X-bits  that  I  regard  it  as 
worthy  of  special  description.  Maj.  Derby  writes  me  that 
he  patented  the  drill  bit  in  1885  and  sold  the  patent  rights 
to  the  Rand  Drill  Co.,  which,  for  reasons  unknown  to  him, 
has  never  placed  it  upon  the  market.  The  drill  steel  was 
hollow,  as  was  also  the  bit  which  was  provided  with  six 
points  or  teeth.  The  bits  were  sharpened  very  much  like  the 
bits  used  in  the  plug  drills  made  by  the  C.  H.  Shaw  Pneu- 
matic Tool  Co.,  of  Denver,  Colo.  Each  bit  was  only  2  to  6 
ins.  long  and  fastened  to  the  end  of  the  hollow  wrought  iron 
drill  rod  with  a  steel  pin  or  expanding  copper  ring.  This  saved 


SUBAQUEOUS  EXCAVATION.  291 

steel  and  saved  transporting  long,  heavy  drill  rods  to  and 
from  the  blacksmith  shop.  This  bit  was  used  with  the' ordi- 
nary percussive  air  drill,  and,  in  drilling,  a  small  core  was 
formed  which  broke  up  under  a  slight  blow  on  the  drill  rod. 
The  chips  were  washed  out  of  the  hole  by  a  current  of  water 
that  was  forced  down  through  the  hollow  drill  rod.  The 
water  was  introduced  into  the  hollow  drill  rod,  either  through 
the  rotating  bar  or  through  a  sleeve  surrounding  the  piston 
rod  which  was  lengthened  for  this  purpose ;  the  first  method 
being  the  best.  Maj.  Derby  informs  me  that  the  coarse 
chips  of  rock  broken  off  by  the  bit  are  washed  out  whole, 
instead  of  being  reduced  to  dust,  which  saves  power  and 
time  in  drilling  a  hole  of  given  depth.  This  fact  is  well 
shown  by  the  following  comparative  records :  Experiments 
were  conducted  for  several  months  of  actual  work,  during 
which  time  39,119  ft.  of  hole  were  drilled  with  X-bits  and 
39,200  ft.  with  the  Derby  tubular  bit.  The  holes  were  about 
9  ft.  deep,  and  Rand  "Little  Giant"  drills  were  used.  As 
a  result  of  this  competition  it  was  found  that  the  tubular 
bit  drilled  51^  per  cent,  faster  than  the  X-bit,  and  that 
the  diameter  of  the  bottom  of  the  hole  was  25  per 
cent,  greater  than  with  the  X-bit,  which  in  itself  is  a  decided 
advantage.  Using  a  starter  X-bit  of  3*4  ins.,  the  bottom  of 
a  lo-ft.  hole  was  2  ins.  diam. ;  but  with  the  tubular  bit  the 
bottom  was  2^2  ins.  diam.  Moreover  the  tubular  bit  made 
a  perfectly  round  hole,  which  lessens  the  chances  of  a  bit's 
sticking.  It  seems  to  me  that  the  greater  speed  of  drilling 
with  the  tubular  bit  was  due  to  the  use  of  a  jet  of  water 
to  wash  out  the  chips,  which  also  accounts  for  the  fact  that 
the  bit  does  not  wear  so  rapidly.  Whatever  the  reason,  the 
record  of  excellence  of  the  tubular  bit  is  well  worthy  of 
serious  consideration  by  all  who  are  interested  in  economic 
drilling. 

Drilling  and  Dredging  Way's  Reef. — Way's  Reef,  New 
York  Harbor,  was  removed  in  1874.  The  crew  was  35  men, 
consisting  of  I  draftsman,  2  divers,  3  carpenters,  I  engineer, 
8  drillers,  I  blaster,  i  blacksmith,  2  blacksmith  helpers,  12 


292        ROCK  EXCAVATION— METHODS  AND  COST. 

sailors,  2  firemen,  I  timekeeper  and  i  tide  gage  keeper. 
This  crew  worked  two  shifts  on  the  U.  S.  steam  drilling 
scow.  At  first  the  starting  bits  were  3^  ins.,  but  later  it 
was  found  that  by  using  a  5^-in.  bit  more  explosive 
could  be  placed  in  a  hole  resulting  in  breaking  the  rock  up 
much  better,  even  with  comparatively  wide  spacing  of  the 
holes,  which  is  a  point  well  worth  remembering.  The 
average  depth  of  drill  hole  was  8.13  ft.,  but  only  6l/>  ft.  of 
hole  were  averaged  per  drill  per  8-hr,  shift.  About  3,030 
cu.  yds.  of  mica-schist  were  excavated,  15,308  Ibs.  of  nitro- 
glycerin  being  used.  The  cost  of  dredging  and  dumping 
the  rock  was  $4.29  per  cu.  yd.,  the  dredge  averaging  35  cu. 
yds.  per  day.  The  total  cost  of  this  excavation  was  $18.26 
per  cu.  yd.  The  work  was  done  by  day  labor  for  the  Govern- 
ment, and  at  a  time  when  subaqueous  drilling  was  an  art 
little  understood. 

Cost  of  Excavation,  Eagle  Harbor,  Mich. — The  following 
facts  have  been  abstracted  from  a  report  by  Mr.  L.  Y.  Scher- 
merhorn :  In  1877  a  dredge  was  used  for  removing  blasted 
rock  in  Eagle  Harbor;  3,200  cu.  yds.  being  dredged  in  63 
days  (lo-hr.)  to  a  depth  of  14  ft.  The  dredge  scow  was 
65  ft.  long,  the  dredge  being  an  "Otis"  with  a  I  cu.  yd.  dip- 
per. The  rocks  handled  by  the  dredge  dipper  averaged  less 
than  I  cu.  ft.  in  size.  Rocks  of  I  cu.  yd.  or  more  were 
chained  out.  The  rock  was  a  trap  and  conglomerate,  weigh- 
ing 169.4  Ibs.  per  cu.  ft. ;  and  I  cu.  yd.  of  solid  rock  made 
1.83  cu.  yds.  of  loose  rock  in  the  scows.  The  rock  dipped 
30°  to  the  north.  Table  XXXVII.  gives  the  data  of  three 
seasons'  work : 

TABLE  XXXVII. 
"o          +J        *d      «  en       •$          Dynamite. 

ol  rt  C 

£  s         J3  0,  eu 

O  *O          +3  rt  o* 

r*  CU  rv  UH 


«         a      -          - 


.c 


1 

C/3 

1875.. 
1876.  . 

I877-. 
Total. 

o 
o 

392 
309 

183 

J_ 

£ 
2,099 

i,945 
1,343 
5.387 

~ 
.13 

5-35 
6.30 
7-34 

•5 

5-0 
7-7 
8-5 

en 

en 

3 
656 
132 

88 
876 

6 

£ 
2.36 
2.67 
2.26 

03 

Q 

51 
40 
32 
123 

en 

"o 

147 
275 
154 

O 

75 
775 
600 

1.450 

of 

6 

441 
3,260 
1,899 

SUBAQUEOUS  EXCAVATION.  293 

Most  of  the  drilling  was  done  from  a  large  platform ;  but 
for  drilling  boulders  a  tripod  platform  was  used,  on  which 
the  drill  was  mounted.  Drill  holes  were  plugged  with  wood- 
en plugs,  but  storms  and  ice  caused  the  loss  of  nearly  two- 
thirds  of  the  holes  drilled  the  first  season  (1875).  One-half 
the  cost  of  drilling  was  chargeable  to  the  first  2  ft.  of  the 
hole;  that  is,  up  to  the  point  where  the  drill  pipe  entered 
the  hole,  protecting  it  from  further  filling  up  with  sand. 
During  the  last  season  (1877)  the  holes  were  drilled  20  ft. 
below  water  surface,  or  about  4^2  ft.  below  the  bottom  of 
the  intended  excavation;  but  a  greater  depth  would  have 
made  the  dredging  easier  by  breaking  up  the  rock  better. 
No.  i  dynamite  broke  the  rock  up  well  for  a  small  area 
around  the  hole;  but  No.  2  broke  the  rock  up  better  for  a 
greater  area.  A  mixed  charge  of  No.  i  and  No.  2  proved 
the  most  effective.  The  following  are  the  data  of  dredg- 
ing :  June  26  to  Sept.  6,  63  days  ;  days  worked,  47 ;  average 
hours  worked  per  day,  I2J4 ;  repairs  made  during  good 
weather,  83  hrs. ;  repairs  made  during  bad  weather,  46  hrs. ; 
rock  dredged  per  hr.,  5.55  cu.  yds.;  rock  dredged  (place 
measure),  3,000  cu.  yds.;  boulders  dredged,  200  cu.  yds.; 
large  rock  chained  out  by  divers,  150  cu.  yds.;  average 
depth  of  solid  rock  excavated,  2.6  ft. ;  maximum  depth  of 
rock,  5.0  ft. ;  area  excavated,  35,000  sq.  ft. 

Cost  of  Eock  Excavation,  Pier  14,  New  York  Harbor.— In 
the  Trans.  Am.  Soc.  C.  E.f  Vol.  XXXII.,  1894,  Mr.  John 
A.  Bensel  describes  the  method  and  cost  of  excavating  1,530 
cu.  yds.  of  mica-schist  near  Pier  14,  New  York  City.  The 
excavation  was  carried  to  35  ft.  below  low  water,  or  40  ft. 
below  high  tide.  A  contractor  began  the  work  at  $25  per 
cu.  yd.,  but  finally  abandoned  the  work.  The  crew  con- 
sisted of  i  diver,  i  foreman,  2  blacksmiths  and  5  deck  hands ; 
and,  drilling  from  a  platform  with  one  Ingersoll  drill 
(largest  size),  they  averaged  only  13^  lin.  ft.  a  shift.  Two 
18  x  2o-ft.  platforms,  floated  out  on  pontoons  and  support- 
ed by  8  x  8-in.  spuds  55  ft.  long,  were  used.  When  stand- 


294        ROCK  EXCAVATION— METHODS  AND  COST. 

ing  on  the  spuds  the  platforms  shifted  up  and  down  stream 
with  the  tides,  3^  ft.  from  the  vertical.  The  platforms  col- 
lapsed three  times ;  once  due  to  swell  of  a  passing  boat ;  once 
due  to  a  blast ;  and  the  third  time  without  apparent  cause. 
While  the  platforms  were  being  repaired,  a  crew  of  2  divers 
and  10  men  removed  85  cu.  yds.  of  the  blasted  rock,  at  the 
rate  of  only  3.4  cu.  yds.  of  loose  rock  per  shift.  Then  a 
grab-bucket  dredge  was  tried;  and  averaged  18  cu.  yds.  of 
loose  rock  a  day  for  a  week.  The  contractor  then  aban- 
doned the  work.  The  Dock  Department  then  built  a  large 
four-drill  scow  of  12  x  12-in.  spruce,  the  dimensions  being 
22  x  33^  ft.  x  6  ft.  deep.  The  scow  and  plant  cost  $5,000. 
This  scow  was  not  provided  with  spuds  (a  fatal  omission), 
but  was  anchored  with  four  pile-driver  hammers  of  3,000 
Ibs.  each.  The  drill  rods  consisted  of  two  pieces  of  i^-in. 
octagon  steel,  joined  by  a  double  ended  chuck  to  make  a 
total  length  of  45  to  50  ft.  From  Sept.  2,  1892,  to  Mar.  13, 
1893,  drilling  was  carried  on  without  interruption  (presum- 
ably working  one  shift  a  day  with  four  drills),  and  only  231 
holes  (2l/2  and  3-in.)  were  drilled,  each  averaging  7  ft.  deep, 
which  was  3  ft.  below  grade.  Gelatin  (95  per  cent.)  was 
used  in  blasting.  In  dredging,  clam-shell  buckets,  4  and  7 
cu.  yds.  capacity,  a  grapple  and  a  bucket  dredge  were  tried, 
with  little  difference  in  results,  all  being  very  disappoint- 
ing. The  solid  rock  dredged  was  1,530  cu.  yds.,  plus  450 
cu.  yds.  of  riprap,  and  it  took  886  hrs.  work  of  the  dredge 
to  do  this  work,  costing  $22,145  f°r  tne  dredging  alone! 
The  amount  of  rock  removed  by  the  dredge  was  4,805  cu. 
yds.,  measured  in  the  scow;  beside  which  480  cu.  yds.  of 
rock  (scow  measure)  were  removed  by  divers.  The  total 
cost  of  this  work  was  nearly  $70,000.  I  think  it  would  be 
hard  to  find  a  better  example  of  money  wasted  in  an  attempt 
to  do  work  by  day  labor  instead  of  by  contract.  The  failure 
of  an  inexperienced  contractor  evidently  led  the  Dock  De- 
partment into  an  expensive  experiment.  Another  feature 
about  this  work  that  showed  lack  of  experience  was  the 


SUBAQUEOUS  EXCAVATION.  295 

failure  to  space  the  holes  closer  together,  or  to  drill  holes 
larger  in  diameter,  or  both.  If  that  had  been  done  the  dredge 
would  have  been  more  effective.  The  mica-schist  of  Man- 
hattan Island  is  an  exceedingly  tough  rock,  and  it  requires 
close  spacing  of  holes  for  subaqueous  work  like  this,  in 
order  to  break  the  rock  into  small  sizes.  The  Dock  De- 
partment, however,  spaced  the  holes  6  ft.  apart  on  the  north 
and  south  lines,  and  5  ft.  apart  on  the  east  and  west  lines, 
according  to  Mr.  Bensel ;  although  according  to  the  scale 
drawings  given  by  him  the  distances  were  5  ft.  and  4  ft.  in- 
stead of  6  ft.  and  5  ft.,  as  stated  in  the  text.  The  result  of 
the  blasting  seemed  to  be  to  stack  the  broken  stones  against 
each  other,  and  not  to  loosen  and  throw  up  the  mass.  Divers 
described  this  bottom  as  being  oftentimes  like  a  pile  of  grave 
stones,  one  stone  lying  against  another. 

Drilling  and  Dredging  Boulders. — The  following  is  an  ab- 
stract from  Engineering  Record,  Jan.  13,  1900:  At  Wood's 
Hole,  Mass.,  large  boulders  were  encountered  in  dredging 
and  were  drilled  from  a  platform  (10  x  25  ft.)  suspended 
from  the  dipper  boom  by  a  tackle  at  each  corner.  Ordi- 
narily the  platform  is  held  by  clamps  which  slide  on  vertical 
clamp  timbers  on  the  bow  of  the  dredge.  If  it  is  desired 
to  swing  the  platform  around  one  end  as  a  center,  it  is 
clamped  to  one  guide  only,  which  is  in  the  middle  or  at  one 
corner.  A  slot  to  drill  through  runs  from  end  to  end  of 
the  platform. 

A  3^2-in.  pipe  has  at  one  end  an  i8-in.  ring  6  ins.  deep 
with  the  annular  space  cast  full  of  babbitt ;  and  this  is  set 
vertically  in  the  slot  of  the  platform.  The  loaded  end  of 
the  pipe  is  set  on  the  highest  point  of  a  boulder,  and,  even 
against  the  strongest  tides,  is  held  in  position  by  its  weight 
and  by  guys  from  the  bottom  to  the  platform.  A  Rand  drill 
is  placed  over  the  pipe  and  its  2%-in.  bit  inserted  in  it.  The 
Rand  drill  is  lowered  by  tackle  when  the  limit  of  its  feed 
is  reached.  For  charging  the  bit  is  replaced  with  a  2-in. 
pipe  and  a  i-in.  cartridge  is  inserted  and  fired  with- 


296        ROCK  EXCAVATION— METHODS  AND  COST. 

out  moving  the  dredge.  An  ordinary  day's  work  with  a 
7-yd.  dipper  dredge  has  been  126  cu.  yds.  of  earth  and  7^/2 
cu.  yds.  of  rock. 

Drilling  in  San  Francisco  Harbor. — The  following  is  an 
abstract  from  Engineering  Record,  May  26,  1900:  In  San 
Francisco  Harbor  ledges  of  metamorphic  sandstone  were 
drilled  from  a  revolving  platform.  The  platform,  25  x  160 
ft.,  is  made  of  four  lines  of  longitudinal  stringers  of  3  x  12- 
in.  timbers  bolted  together.  These  stringers  rest  on  8  x  10 
in.  floor  beams  that  are  20  ft.  c.  to  c.,  and  queen-post  trussed. 
Through  the  center  of  the  platform  rises  a  mast  2  ft.  square 
and  68  ft.  high,  made  of  four  pieces  of  12  x  12-in.  bolted 
together  and  dressed  to  a  diameter  of  18  ins.  for  the  upper 
15  ft.  The  top  of  the  mast  is  guyed  by  four  wire  cables 
to  anchors.  One  block  of  a  tackle  is  clamped  to  the  upper 
end  of  each  guy;  the  other  block  is  attached  to  the  top  of 
the  mast,  and  enables  the  guys  to  be  tightened  or  adjusted 
readily.  Fifteen  feet  below  the  top  of  the  mast  there  is 
fixed  to  it  a  collar  with  a  channel  in  its  upper  surface,  in 
which  there  are  steel  balls  for  the  bearings  of  a  revolving 
collar  above,  to  which  are  attached  18  guys  (i-in.),  or  sup- 
ports, one  to  each  end  of  each  of  the  nine  floor  beams.  These 
guys  are  adjusted  by  long  turn-buckles  at  the  bottom.  Two 
steam  drills  and  one  well  driller  a*re  installed  on  the  plat- 
form and  operate  lo-in.  bits.  The  holes  are  cased  with  10- 
in.  sheet  iron  pipe.  Steam  boilers  are  located  on  a  barge 
and  deliver  steam  through  ball  and  socket  pipe. 


CHAPTER  XVI. 
COST   OF   RAILWAY   TUNNELS. 

The  American  System. — In  America  there  is  to-day  only 
one  system  of  rock  tunneling  in  common  use.  The  Amer- 
ican system  has  four  distinctive  features :  ( I )  An  advance 
tunnel  called  a  "heading"  is  driven  in  the  upper  part  of  the 
proposed  tunnel.  (2)  The  drill  holes  in  the  center  of  the 
heading  converge  in  pairs,  forming  a  V,  and  are  fired  first 
so  as  to  form  a  wedge-shaped  cut,  called  the  "center  cut." 

(3)  The  lower  part  of  the  tunnel,  called  the  "bench,"  is 
taken  out  by  blasting  in  holes  drilled  vertically,  or  nearly  so. 

(4)  Timbering,  if  used  at  all  to  support  the  roof,  consists  of 
"bents,"  each  having  upright  posts  supporting  a  segmental 
wooden  arch,  upon  which  rests  longitudinal  planking,  called 
"lagging." 

Two  of  these  four  features  appear  unquestionably  to  have 
been  invented  by  Americans.  The  center-cut  system  of  drill- 
ing was  first  used  in  the  celebrated  Hoosac  Tunnel  in  Mass- 
achusetts (begun  1858)  ;  and  the  segmental  arch  system 
of  timbering,  which  leaves  the  entire  area  of  the  tunnel  un- 
obstructed by  props  or  supports  of  any  kind,  was  first  used 
in  1854  in  the  Van  Nest  Gap  Tunnel,  on  the  D.,  L.  &  W. 
R.  R.,  in  New  Jersey,  under  Mr.  James  Archibald,  Chief 
Engineer.  Three  rafter  pieces  had  been  used  in  American 
tunnels  prior  to  1854,  but  to  Mr.  Archibald  belongs  the 
credit  of  having  increased  the  number  so  as  to  make  a  regu- 
lar wooden  arch.  This  system  of  timbering  has  been  suc- 
cessfully used  even  in  tunneling  through  sand  and  gravel, 
and  it  is  an  open  question  whether  any  of  the  cumbersome 
systems  used  abroad  need  ever  be  used  in  America. 

Occasionally  some  contractor  tries  an  experiment  such 
as  driving  the  "heading"  at  the  bottom  instead  of  at  the 

297 


2Q8        ROCK  EXCAVATION— METHODS  AND  COST. 

top.  After  killing  a  few  men,  return  is  usually  made  to 
the  top  heading.  It  is  exceedingly  difficult,  and  in  loose 
rock  impossible,  to  prevent  disastrous  falls  of  rock  from 
the  roof  where  the  bottom  heading  method  is  used.  One 
contractor,  an  eminent  member  of  the  American  Society  of 
Civil  Engineers,  had  his  life  crushed  out  by  a  fall  of  rock 
in  a  tunnel  that  he  was  driving  in  New  York  City  by  the 
bottom  heading  method. 

Fig.  51  shows  the  American  system  of  timbering. 

When  machine  drills  were  first  used  in  tunneling  it  was 
thought  necessary  to  mount  the  drills  on  drill  carriages 
which  ran  upon  tracks.  The  delays  involved  in  clearing 
away  the  muck  (as  the  broken  rock  is  called)  so  that  the 
drill  carriage  could  be  run  up  to  the  face  again  after  blast- 
ing, led  to  the  invention  of  the  column  method  of  mounting 
drills.  Two  drills  may  be  mounted  on  opposite  sides  of  one 
column,  and  I  have  seen  two  columns  with  four  drills  used 
in  a  heading  10  ft.  wide.  Two  drills  on  one  column,  how- 
ever, cannot  be  worked  to  advantage  in  a  heading  much 
less  than  6l/>  ft.  wide. 

With  four  drills  at  work  the  holes,  which  are  usually  8 
to  12  ft.  deep,  are  drilled  in  a  heading  with  great  rapidity : 
but  the  time  lost  in  waiting  for  smoke  to  clear  away  after 
blasting,  and  in  mucking  (loading  the  rock),  usually  con- 
sumes 50  per  cent,  of  the  total  time.  In  railway  tunneling 
rapid  progress  is  usually  imperative,  and  this  is  especially 
true  where  tunnels  are  so  long  that  the  rest  of  the  construc- 
tion work  will  be  completed  ahead  of  the  tunnel  work.  To 
overcome  the  delays  incident  to  blasting  and  mucking,  the 
contractor  should  spare  no  reasonable  expense  where  rapid 
progress  is  desired ;  yet  one  of  the  commonest  errors  is  to 
provide  no  adequate  means  for  clearing  the  air  after  blast- 
ing. I  have  described  the  Simplon  Tunnel  work  in  some 
detail,  because  I  think  that  American  contractors  are  not, 
as  a  rule,  awake  to  the  advantage  of  using  water  under 
pressure  to  lay  the  dust  and  the  smoke,  in  addition  to  using 


COST  OF  RAILWAY  TUNNELS. 

properly  designed  fans  or  blowers.  Another  lesson  that  can 
be  learned  from  the  Simplon  Tunnel  is  the  use  of  sheet  iron 
covering  laid  down  upon  the  car  rails  before  blasting.  By 
doing  this  it  is  possible  for  the  muckers  to  clear  the  track 
quickly  after  a  blast,  so  as  to  get  muck  cars  up  to  the  face 
without  delay.  A  third  lesson  to  be  learned  is  the  use  of  shal- 
low holes  with  very  heavy  charges  of  explosive.  This  causes 
the  muck  to  be  broken  up  fine  and  to  be  hurled  away  from 
the  face,  so  that  it  takes  the  minimum  of  time  to  clear  the 
face  ready  to  begin  drilling.  I  repeat  that  the  contractor 
who  seeks  to  make  a  record  in  rapid  tunneling  should  bend 
every  effort  to  provide  ways  and  means  for  the  rapid  clear- 
ing of  muck,  gas  and  dust  away  from  the  face,  so  as  to  keep 
the  drills  at  work  as  large  a  percentage  of  the  time  as  pos- 
sible. 

A  Device  for  Laying  the  Dust  with  Water. — Where  a  long 
tunnel  is  to  be  driven  it  will  unquestionably  pay  to  have 
a  water  main  laid  alongside  the  air  main,  so  as  to  deliver 
a  stream  of  water  against  the  face  after  a  blast ;  but  in  short 
tunnels  it  may  not  pay  to  do  this.  A  device  that  has  been 
used  with  success  in  England  by  Mr.  William  James  is  de- 
scribed in  a  paper  read  May  19,  1904,  before  the  Institution 
of  Mining  and  Metallurgy.  As  originally  designed  it  con- 
sists of  a  length  of  6-in.  pipe,  which  is  let  into  the  2-in.  air 
main  at  the  mouth  of  the  level  (in  a  mine).  This  6-in.  pipe 
is  provided  with  a  tap,  through  which  it  can  be  filled  with 
water  from  a  cistern  just  before  blasting.  After  blasting 
a  compressed  air  valve  is  suddenly  opened,  and  the  water 
is  carried  by  the  air  in  the  form  of  a  fine  spray  out  of 
the  air  pipe,  which  is  directed  against  the  face.  The  result 
is  that  for  40  ft.  back  of  the  face  the  dust  and  nitrous  fumes 
are  quickly  laid  by  the  water.  A  ventilation  pipe  into  which 
air  jets  are  delivered  quickly  sucks  out  the  CO  and  CO2 
gases,  thus  leaving  a  face  clear  of  dust  and  gases. 

The  Gallitzin  Tunnel.— This  is  a  single-track  tunnel,  3,600 
ft,  long,  through  the  Alleghenies,  on  the  line  of  the  Penn- 


300        ROCK  EXCAVATION— METHODS  AND  COST. 

sylvania  R.  R.  The  work  was  done  in  the  years  1903  and 
1904,  under  contract,  by  Mr.  P.  F.  Brendlinger,  M.  Am. 
Soc.  C.  E.,  who  was  kind  enough  to  give  me  every  facility 
for  studying  it.  The  material  encountered  was  mostly  shale 
and  some  sandstone.  Figs.  48  and  49  show  the  tunnel  di- 
mensions and  the  placing  of  drill  holes.  For  the  most  part 
no  timbering  was  required.  Two  portal  headings  were 


Fig. 


Fig.  49. 


driven,  there  being  no  shafts.  In  each  heading  there  were 
four  air  drills  mounted  on  two  columns.  Headings  were 
at  first  7  ft.  high  and  15  ft.  wide,  but  were  gradually  nar- 
rowed, to  10  ft.  wide.  Each  driller  was  given  a  day's  stint 
of  four  lo-ft.  holes  in  the  lo-ft.  heading,  although  when 
the  heading  was  15  ft.  wide  five  holes  was  a  shift's  work  per 
drill.  The  heading  force  began  work  at  7  A.  MV  but  drilling 
did  not  usually  begin  before  8  A.  M.,  and  was  finished  by  3 
p.  M.  The  holes  were  loaded  and  fired  by  4  P.  M.  The  drill- 
ing force  on  each  heading  consisted  of  4  drillers,  4  helpers, 
I  nipper  (or  tool  carrier),  I  mucker,  I  timberman,  i  powder- 
man  and  I  foreman,  a  total  of  13  men.  The  night  shift 
on  the  heading  consisted  of  14  muckers,  I  foreman,  with  2 
mules  hauling  the  dump  cars  to  the  bench,  which  was  never 
more  than  1,000  ft.  back  of  the  face.  At  the  bench  the 
muck  was  dumped  and  loaded  by  a  steam  shovel,  together 
with  the  bench  muck,  into  cars  hauled  away  by  a  dinkey 


COST  OF  RAILWAY  TUNNELS. 


301 


locomotive.  Although  the  holes  in  the  heading  face  were 
10  ft.  deep,  the  actual  advance  after  each  blast  was  9  ft. 
The  6  "cut  holes"  were  fired  first,  then  the  side  holes  on 
one  side,  then  the  side  holes  on  the  other  side,  and  finally 
the  roof  holes,  making  four  separate  shots  for  the  16  holes. 
Each  hole  was  charged  with  14  sticks  of  40  per  cent.  Forcite 
gelatin,  using  three  boxes  for  a  charge.  Each  firing  threw 
down  about  23  cu.  yds.,  hence  there  were  7  ft.  of  drill  hole 
and  6l/2  Ibs.  of  Forcite  per  cu.  yd.  of  heading.  The  muck 
was  broken  into  small  fragments  by  the  blast.  Each  muck- 
er averaged  less  than  2  cu.  yds.  loaded  per  shift.  The  aver- 
age progress  was  50  ft.  of  heading  a  week  at  each  end  of 
the  tunnel,  working  as  described. 


Fig.  50. 

The  bench  was  taken  out  in  two  lifts,  as  shown  in  Fig. 
49.  Two  or  three  drills  on  tripods  first  drill  holes  to  widen 
out  the  heading.  In  the  top  bench  four  vertical  holes  are 
driven  7  ft.  deep,  and  two  diagonal  holes,  about  7  ft.  back 
of  the  face.  The  bottom  bench  holes  are  placed  12  to  14 


302       ROCK  EXCAVATION-METHODS  AMD  COST, 

ft.  back  of  the  face.  The  four  vertical  holes  in  the  top 
bench  are  "sprung"  by  firing  I  to  il/2  sticks  in  each  hole, 
and  then  loaded  with  5  to  8  sticks  per  hole.  The  holes  in 
the  bottom  bench  were  "sprung"  twice ;  first  with  two  sticks 
per  hole,  then  with  10  to  14  sticks,  and  finally  loaded  with 
40  to  60  sticks  in  each  hole.  About  1,000  Ibs.  of  Forcite 
were  used  per  month  in  both  ends  of  the  tunnel.  The  steam 
shovel  was  run  with  compressed  air,  and  was  used  in  this 
single-track  tunnel  with  economy.  The  tunnel  was  lined 
with  rubble  bench  walls  and  a  concrete  arch,  as  shown  in 
Fig.  50.  Space  forbids  going  into  greater  detail. 


Fig.  51- 

Wabash  R.  R.  Tunnels. — I  am  indebted  to  Mr.  T.  H. 
Loomis,  Div.  Eng.  P.,  T.  &  W.  R.  R.  (Wabash  system)  for 
much  of  the  following  data  kindly  furnished  by  him  when 
I  went  over  the  line  in  1903  studying  the  methods  and  cost 
of  excavation.  Eight  double-track  tunnels  were  underway, 
the  cross-section  of  each  being  as  shown  in  Fig.  51.  The 
material  encountered  was  shale,  sandstone,  fire  clay  and 
occasional  seams  of  coal — characteristic  of  eastern  Ohio 
and  western  Pennsylvania.  The  section  above  the  wall 
plates  (*.  e.,  the  longitudinal  timbers  on  top  of  the  posts) 
requires  an  excavation  of  15  cu.  yds.  per  lin.  ft.  The  clear 
width  between  wall  plates  is  3454  ft.  The  segmental  arch 


COST  OF  RAILWAY   TUNNELS.  303 

timbers  are  12  x  12  ins.,  lagged  with  4-in.  plank,  the  arch 
ribs  being  3  to  4  ft.  c.  to  c.  The  favorite  method  of  attack, 
as  shown  in  Fig.  52,  was  by  what  I  will  term  the  twin-head- 
ing method ;  two  7  x  8  f t.  headings  being  driven  as  shown, 
and  afterward  enlarged.  The  floor  of  these  headings  is  i2l/2 
ft.  above  subgrade,  thus  leaving  a  12^-ft.  bench,  A  C  D  E, 
to  be  taken  out.  One  machine  drill  is  operated  in  each  head- 


fire  Clay- 


+£r  pr-j 

A[ i -i- 


Fig.  53- 

ing  (two  could  be  worked)  for  the  drilling  is  easy.  The 
rivalry  between  the  two  drilling  gangs  in  these  twin  head- 
ings appeared  to  me  to  be  one  of  the  best  features  of  this 
method  of  attack.  It  is  certain  that  no  hitherto  published 
data  show  as  low  a  cost  per  cubic  yard  for  tunnel  work  as 
the  data  which  I  secured  on  this  work.  The  weekly  prog- 
ress was  not  rapid,  but,  as  all  the  tunnels  were  comparative- 
ly short,  there  was  no  necessity  of  going  to  great  expense, 
in  securing  rapid  progress — a  fact  that  tunnel  contractors 
should  bear  in  mind.  Steam  drills  were  used  in  some  of  the 
short  tunnels.  The  following  is  the  actual  cost  of  excavat- 
ing and  timbering  the  section  of  a  tunnel  above  the  wall 
plates  (15  cu.  yds.  per  lin.  ft),  using  air  drills,  for  a  dis- 
tance of  100  lin.  ft. : 

Labor   $2,527.45 

2,000  Ibs.  40  p.  c.  dynamite  at  12  cts 260.00 

470  gals,  kerosene  oil,  at  12  cts 56.40 

1,875  gals-  gasoline,  at  12  cts 225.00 

3,000  bu.  coal  for  compressor,  at  9  cts 270.00 

Machine  and  lub.  oils   62.50 

Blacksmith   shop     : 150.00 


304        ROCK  EXCAVATION— METHODS  AND  COST. 
41,649  ft.  B.  M.  timber,  at  $23  $957-93 


Total  cost  of  100  lin.  ft $4,509.28 

Cost  per  lin.  ft.  above  wall  plates 45.09 

Cost  per  cu.  yd.,  including  timber 3.06 

Cost  per  cu.  yd.,  excluding  timber 2.60 

The  material  in  this  case  was  sandstone. 
On  another  tunnel  the  section  above  the  wall  plates  was 
excavated  by  hand  at  a  cost  $40.90  per  lin.  ft.,  or  $2.73  per 
cu.  yd.,  for  a  distance  of  no  ft.,  the  material  being  hard 
fire  clay  in  the  upper  half  and  shale  in  the  lower  half  of 
the  section  excavated,  making  easier  excavation  than  in  the 
sandstone.  The  force  engaged  in  hand  drilling,  by  the  twin- 
heading  method,  was: 

Wages  per 
10-hr,  shift. 

i  general  foreman   $4 

i   foreman    3 

1  blacksmith    3 

2  carpenters,  at  $3  6 

10  miners,  at  $2 20 

10  muckers,  at  $1.50  15 

i  team   4 

Total  per  shift  (zo-hr.)   $55 

While  these  men  took  out  the  whole  section  above  the  wall 
plates  (15  cu.  yds.  per  lin.  ft.)  for  $2.73  per  cu.  yd.  for  labor 
and  explosives  (not  including  cost  of  timber),  working  in 
shale  and  fire  clay,  they  excavated  a  7  x  8-ft.  heading  in 
sandstone  for  $3.75  per  cu.  yd.,  distributed  as  follows : 

Per  lo-hr.  shift. 

Labor  on  7  x  8  heading $18.00 

Dynamite    3.84 

Repairs    90 

Light 32 

Total  per  shift $23.06 


COST  OF  RAILWAY  TUNNELS.  305 

Each  shift  excavated  6.2  cu.  yds.  of  this  7  x  8.-ft.  heading, 
making  the  cost  $375  per  cu.  yd.,  as  above  stated,  equiva- 
lent to  an  advance  of  3  ft.  per  shift. 

No  night  shifts  were  being  worked  on  the  eight  tunnels, 
and  the  progress  per  week  in  shale  was  25  ft.  when  work- 
ing by  hand  and  excavating  15  cu.  yds.  per  lin.  ft.;  and  50 
ft.  a  week  working  with  machine  drills.  In  hard  sandstone 
the  weekly  progress  was  about  15  ft.  by  hand  and  30  ft.  with 
machine  drills,  in  all  cases  working  only  one  xo-hr.  shift 
in  the  24-hr,  day. 

The  following  is  the  actual  cost  of  timbering  on  one  job : 

Per  M. 

Georgia  pine  f.  o.  b.  cars $23.60 

Hauling  6  miles   3.00 

Cost  of  framing  5.00 

Cost  of  erecting 3.00 


Total  per  1,000  ft.  B.  M $34-6o 

The  carpenters  received  $3  per  lo-hr.  day,  and  laborers 
erecting  received  $1.50.  The  cost  of  framing  and  erecting, 
including  supervision,  was  $8  per  M.,  which  was  about  $2 
more  than  it  should  have  cost  had  there  been  more  workers 
and  fewer  bosses.  Over  the  rough  roads  each  team  hauled 
about  1,000  ft.  B.  M.  per  load  and  made  one  trip  of  6  miles 
each  way  in  a  day.  The  cost  of  "packing"  (i.  e.,  placing 
small  stones)  above  the  lagging  was  80  cts.  per  cu.  yd. 

We  now  come  to  what  I  have  said  are  the  lowest  records 
of  tunneling  cost  yet  made  public: 

Tunnel  heading  in  sandstone,  double  track  full  section 
above  the  wall  plate  grade  (15  cu.  yds.  per  lin.  ft.)  : 

Cu.  yd. 

Drilling   $0.60 

Explosives 40 

Mucking 85 


Total    $1.85 


306       ROCK  EXCAVATION— METHODS  AND  COST, 

Tunnel  bench  in  same  tunnel: 

Cu.  yd. 

Drilling $0.40 

Explosives   20 

Mucking   22 


Total    $0.82 

The  sandstone  was  very  hard,  breaking  in  large  blocks, 
which  have  to  be  drilled  and  shot  before  mucking.  A  steam 
shovel  is  used  in  the  bench,  and  material  of  heading  is  car- 
ried about  400  ft.  and  dumped  over  the  breast  of  bench, 
whence  steam  shovel  loads  it  along  with  bench  material. 

In  another  tunnel,  in  a  formation  of  practically  level  strata 
of  slate,  limestone  (thin)  and  fire  clay  (a  stone  hard  as 
limestone  to  drill,  but  disintegrating  in  the  air)  the  cost  was 
as  follows: 

Heading — full  double-track  sections — all  above  walll 
plates : 

Cu.  yd. 

Drilling   $0.48 

Explosives    , 30       « 

Mucking 80 


Total    $1.58 

Bench — same  tunnel — full  section  : 

Cu.  yd. 

Drilling   $0.30 

Explosives    20 

Mucking 18 


$0.68 

In  the  case  of  another  tunnel  in  coal  formation  with  a  5~ft. 
vein  of  coal  running  all  through  on  the  wall  plate  grade; 
steam  drills  used  in  rock,  and  steam  coal  augers  in  the  coal, 
with  steam  shovel  for  mucking,  the  costs  were  as  follows :. 


COST  OP  RAILWAY  TUNNELS, 

Headings — per  cubic  yard — double  track: 

Labor $0.966 

Explosives  and  materials 090 

Total   $1.056 

Bench — same  tunnel  and  formation: 

Cu.  yd. 

Labor $0.38 

Explosives  and  materials 04 


Total    , $0.42 

This  last  may  seem  too  low,  but  it  was  in  all  probability  the 
cheapest  material  a  tunnel  is-  ever  built  in,  and  the  organiza- 
tion was  so  good  that  it  was  worked  with  extreme  economy. 
A  core  of  about  2  cu.  yds.  per  lin.  ft.  was  left  in  the  middle 
of  the  heading  (between  the  twin  headings)  and  taken  out 
along  with  the  bench. 

The  Stampede  Tunnel. — In  Engineering  News,  Oct.  3, 
1891,  Mr.  Charles  W.  Hobart  gives  data  on  the  Stampede 
or  Cascade  Tunnel  of  the  Northern  Pacific  R.  R.  Bids  were 
opened  in  New  York  Jan.  21,  1886,  for  a  2-mile  tunnel  to  be 
completed  in  28  mos.  Of  the  12  bids,  that  of  Mr.  Nelson 
Bennett  was  lowest  and  was  accepted.  A  forfeit  of  $100,000 
and  10  per  cent,  of  the  contract  price  for  failure  to  complete 
within  the  time  was  required.  Mr.  Bennett  telegraphed 
his  general  manager  to  gather  men  and  clear  a  road  to  get 
the  machinery  on  the  ground.  The  plant  was  purchased  for 
$100,000  in  New  York  and  shipped.  It  consisted  of  5  en- 
gines, 2  water  wheels,  5  air  compressors,  5  boilers  of  70- 
H.-P.  each,  4  fans,  2  electric  arc  light  plants,  2  miles  of  6-in. 
wrought  iron,  2  miles  of  water  pipe,  2  machine  shop  outfits, 
36  air  drills,  2  locomotives,  60  dump  cars,  2  saw  mills  and 
other  necessaries.  This  plant  had  to  be  transported  on 
wagons  and  sleds  from  Yakima,  Wash.,  a  distance  of  82 
miles  to  the  east  portal  of  the  tunnel  and  87  miles  to  the 
west  portal.  The  first  wagon  loads  started  Feb.  I,  and  the 


308        ROCK  EXCAVATION— METHODS  AND  COST. 

first  boiler  Feb.  22.  By  June  19  the  plant  for  the  east  portal, 
and  by  July  15  the  plant  for  the  west  portal  had  reached  its 
destination.  On  Feb.  13  hand  drilling  was  begun  on  the 
east  portal  and  411  ft.  of  tunnel  had  been  driven  when  the 
machines  began  June  19.  On  March  15  hand  drilling  start- 
ed at  the  west  end  and  by  Sept.  i,  when  the  machines  start- 
ed, 488  ft.  had  been  driven.  The  last  15  miles  of  the  haul- 
ing before  reaching  the  mountains  was  in  mud,  so  that 
wagons  were  hauled  by  block  and  tackle,  planks  being  laid 
down  in  front  of  the  wheels  and  taken  up  as  fast  as  the 
wagons  passed.  About  one  mile  a  day  was  covered  in  this 
way.  When  the  mountains  were  reached  sleds  were  im- 
provised and  hauled  by  block  and  tackle  with  teams.  Wagons 
lightly  loaded  with  provisions  traveled  12  miles  a  day. 

The  cost  of  clearing  the  way  and  getting  the  machinery 
and  materials  on  the  work  was  $125,000,  *  and  6  mos.  time 
was  required.  The  tunnel  was  to  be  9,950  ft.  long,  16^  x 
22  ft.  in  the  clear ;  900  ft.  had  been  driven  by  hand,  leaving 
9,050  ft.  to  be  driven  in  22  mos. 

An  8-ft.  heading  was  driven  along  the  top  of  the  tunnel 
and  was  kept  30  ft.  ahead  of  the  bench.  The  tunnel  was 
timbered  as  work  progressed.  The  average  number  of  men 
employed,  after  the  machinery  was  installed,  was  350.  They 
worked  lo-hr.  shifts,  receiving  $2.50  to  $5  a  day.  Con- 
tractor boarded  men  at  75  cts.  a  day.  A  bonus  of  25  cts.  a 
day  was  paid  each  laborer  for  every  foot  gained  during  the 
month  over  the  necessary  average  of  13.6  ft.  a  day  in  both 
headings  combined,  and  each  driller  received  a  bonus  of 
50  cts.  per  day  per  ft.  gained.  Every  day  of  the  year  was 
worked,  requiring  two  shifts  of  75  men  each,  beside  the  en- 
gineers, firemen,  carpenters,  machinists,  etc.,  making  a 
monthly  payroll  of  $30,000.  The  best  month's  progress  was 
April,  1888,  when  a  total  advance  of  540  ft.  was  made  in  the 
two  headings,  or  9  ft.  a  day  per  heading.  The  average 
progress  for  21  2/3  mos.,  with  power  drills,  was  413  ft.  per 

NOTE. — Wages  were  $2.50  for  laborers,  which  is  an  unusually  high  price. 


COST  OF  RAILWAY   TUNNELS.  309 

month  for  the  two  headings.  On  May  3,  1888,  the  headings 
met,  and  on  May  14  the  excavation  was  completed,  7  days 
before  the  time  limit.  The  track  was  laid  in  two  days  more 
and  on  May  22  the  first  regular  train  passed  through  the 
tunnel. 

The  total  explosives  used  were  309,625  Ibs.,  as  follows : 

No.  of  5o-lb.  boxes. 

Giant  No.  i,  60  per  cent 4O324 

Giant  No.  2,  45  per  cent 2,123^ 

Hercules  No.  I,  60  per  cent 1,609^ 

Hercules  No.  2,  45  per  cent 1,781 24 

Nitro  glycerin  No.  2   232 

Forcite  No.  2  .  4i/^ 


Total  No.  of  50-lb.  boxes  6,192 

The  average  price  of  all  explosives  was  $10  a  box,  or  20 
cts.  per  Ib.  The  total  number  of  men  killed  in  the  two  years 
was  13.  The  following  data  were  furnished  by  Mr.  An- 
drew Gibson,  Asst.  Engr.  The  American  center-cut  system 
of  blasting  was  used ;  20  to  23  holes,  12  ft.  deep,  being  drilled 
in  the  heading,  and  about  18  holes  in  the  bench.  Each  drill, 
in  medium  hard  rock,  would  make  6  or  7  holes  in  5  hrs., 
although  at  times  in  an  exceedingly  hard  layer  15  hrs.  would 
be  required.  About  400  Ibs.  of  dynamite  were  used  at  each 
blast  in  each  of  the  headings  and  benches.  This  would  break 
8  to  12  lin.  ft.  of  tunnel,  although  in  very  hard  rock  at  times 
only  half  this  progress  was  made.  The  rock  is  basaltic,  * 
with  a  dip  of  5°  to  the  west.  It  required  immediate  tim- 
bering, which  delayed  the  drillers  and  muckers  about  25  per 
cent,  of  the  time.  During  the  period  of  hand  drilling  there 
were  17  men,  with  about  23  muckers,  employed  in  each  head- 
ing, and  4  lin.  ft.  of  tunnel  in  24  hrs.  were  averaged.  Dur- 
ing the  period  of  air  drilling,  10  drills  were  used,  5  in  each 
end,  and  the  progress  was  6.9  ft.  in  24  hrs.  per  heading,  or 
207  ft.  per  mo.  of  30  days.  While  the  contract  size  of  the 
tunnel  was  i6l/2  ft.  wide,  and  22  ft.  from  subgrade  to  face 

*  Elsewhere  it  is  stated  that  the  rock  was  shale. 


310        ROCK  EXCAVATION— METHODS  AND  COST. 

of  arch,  the  timbered  sections  had  to  be  excavated  19^  ft. 
wide  by  24  ft.  high,  thus  requiring  15.7  cu.  yds.  of  excava- 
tion per  lin.  ft.  where  timbering  was  used,  as  against  12.36 
cu.  yds.  where  no  timber  was  used.  Timbers  were  12  x  12 
ins.,  except  the  8  x  12-in.  sills.  Five  segments  were  used 
in  the  arch,  lagged  with  4  x  6-in.  pieces.  Bents  were  spaced 
2  to  4  ft.  Water  gave  no  trouble. 

Mules  were  used  for  hauling  up  to  the  first  half  mile ; 
then  small  locomotives,  which  hauled  8  to  12  cars.  A  "go- 
devil"  or  platform  on  wheels  was  used  to  great  advantage  in 
loading  cars.  The  men  wheeled  the  rock  on  plank  runways 
from  the  heading  to  the  "go-devil,"  dumping  directly  into 
cars  below;  and  the  muckers  on  the  heading  never  inter- 
fered with  those  on  the  bench.  It  was  also  a  great  con- 
venience in  timbering.  Before  blasting  the  drills  were  load- 
ed upon  the  "go-devil,"  and  it  was  pushed  back  some  dis- 
tance from  the  face.  Endless  belt  conveyors  for  removing 
muck  to  the  "go-devil"  were  contemplated,  but  they  were 
never  used,  as  with  the  large  force  of  men  at  work  they 
would  have  been  in  the  way. 

The  swelling  of  the  shale  on  exposure  often  reduced  a 
12-in.  timber  to  4  ins. ;  hence  it  was  necessary  to  line  the 
tunnel  with  masonry.  Concrete  side  walls  and  a  brick  arch 
were  used  for  lining.  The  concrete  mortar  was  brought  in 
on  cars  and  run  back  of  the  forms  through  spouts,  without 
shoveling ;  then  the  broken  rock  was  shoveled  into  the  mor- 
tar from  a  flat  car. 

The  total  cost  of  the  tunnel  to  the  N.  P.  R.  R.  under  Mr. 
Bennett's  contract  (which  di'd  not  include  masonry  lining) 
was  $118  per  lin.  ft.  Mr.  Bennett *s  brother  was  the  super- 
intendent of  the  work.  The  actual  cost  of  tunneling  the 
west  end  during  the  month  of  Nov.,  1887,  was  $75-75  Per 
ft.  for  the  258  ft.  driven,  distributed  as  follows: 

Labor. 
Supt.,  y2  mo.,  at  $500 $250.00 

"      i  mo.,  at  $250 250.00 

Master  mechanic,  y2  m<a.,  at  $150  »«.«««««*«« ?5-Qc> 


COST  OF  RAILWAY   TUNNELS.  311 

Engineers,  4  x  30  =  120  days  at  $4 $480.00 

Machine  repairers,  3  x  30  =    90  days  at  $3.50  ....    315.00 

Firemen  4x30=120     "      "     2.50....    300.00 

Blacksmiths  2  x  30  =    60     "      "     4.00  ....    240.00 

helpers  2x30=    60     "      "     2.50....     150.00 

Carpenters      396  days  at  $3.00 i,  188.00 

Foremen         160     "       "     4.50 720.00 

Drillmen         294     "       "     3.50 1,029.00 

Chuckmen      293     "       "     3.00 579-O° 

Muckers       1,138     "       "     2.75 3,129.50 

Nippers  60     "       "     2.50 150.00 

Dumpmen         60     "       "     2.50 150.00 

Car  drivers       60     "       "     2.50 150.00 

Time  keeper     30     "       "     2.50. 75-OO 

Lampmen          60     "       "     2.50 150.00 

Laborers         662     "       "     2.50 . .  1,655.00 

Bonus  for  daily  progress  over  6  ft 800.00 


Total  labor  for  258  ft.  at  $45.90  per  ft $11,835.50 

Material. 

78,000  ft.  B.  M.  timber,  at  $10 $780.00 

800  Ibs.  wrt.  iron,  at  6  cts 48.00 

64^2  cords  wood,  at  $3 J93-5O 

240  tons  coal,  at  $4 960.00 

900  caps,  at  i  ct 9.00 

14,400  ft.  fuse,  at  i  ct 144.00 

13,800  Ibs.  dynamite,  at  16  cts 2,208.00 


Total  materials  for  258  ft.,  at  $16.80 

per  ft $4,342.50 

Plant. 

6  per  cent,  of  $50,000  plant,  I  mo $250.00 

1/28  of  75  p.  c.  depreciation  *  of  $50,000  plant 1,339.28 

10  p.  c.  on  all  above  to  cover  all  possible  omissions.  11,776.72 


Total  plant  charges  for  258  ft.  at  $13.05 $3,366.00 

*  Note  that  a  liberal  hut  not  unusual  allowance  is  made  for  plant  depreciation,, 
^  ThJs  10  per  cent,  practically  cove.rs_  tb,e.  cQst  qf  installing  th,e  plant. 


312        ROCK  EXCAVATION— METHODS  AND  COST. 

Summary  of  cost  per  ft. 

Labor $45.90 

Material 16.80 

Plant    13.05 


Total   $75.75 

During  this  month  the  entire  length  was  lined  with  timber, 
the  rock  being  a  soft  basaltic  rock  that  drills  well  but  goes 
to  pieces  rapidly  on  exposure.  There  were  no  accidents  or 
delays. 

On  the  east  end  during  this  same  month,  with  an  equal 
force,  the  progress  was  246  ft.,  at  a  cost  of  $72.70  per  ft. 
It  will  be  noted  that  wages  were  high.  It  will  also  be  noted 
that  the  cost  of  hauling  and  installing  the  plant  is  not  in- 
cluded, although  a  liberal  allowance  is  made  for  plant  de- 
preciation and  in  the  10  per  cent,  added  to  cover  omissions. 
The  contractor  received  for  his  month's  work  on  the  west 
end  of  the  tunnel : 

258- ft.  tunnel,  standard  section,  at  $78 $20,124 

862  cu.  yds.  extra  excav.,  at  $4.50 3,879 

78,000  ft.  B.  M.  lining,  at  $35 2,730 


258  ft.  of  tunnel,  timbered,  at  $103.62 $26,733 

The  best  month's  record  in  driving  a  heading  was  274  ft., 
but,  as  before  stated,  the  average  progress  with  the  air  drills 
was  207  ft.  per  mo.  per  heading,  although  in  the  month  of 
Nov.,  1887,  258  ft.  were  progressed  on  the  west  end,  which 
was  25  per  cent,  better  than  the  average  progress.  Assuming 
that  15.7  cu.  yds.  were  excavated  per  lin.  ft.  of  tunnel,  the 
total  excavation  at  the  west  end  for  November  was  4,052  cu. 
yds.  It  is  probable  that  the  862  cu.  yds.  extra  excavation, 
above  given,  are  included  in  this  estimate,  because  the  "stand- 
ard section"  differed  from  the  timbered  section  by  3.3  cu. 
yds.  per  lin.  ft.,  and  in  258  ft.  this  would  amount  to  852  cu. 
yds.  On  this  assumption  (of  4,052  cu.  yds.)  the  labor  cost 
$2.92  per  cu.  yd.;  the  materials,  $1.07  per  cu.  yd.;  and  the 


COST  OF  RAILWAY   TUNNELS.  313 

plant,  $0.83  per  cu.  yd. ;  total,  $4.82  per  cu.  yd.  for  the  best 
month's  work. 

Mount  Wood  and  Top  Mill  Tunnels.— Mr.  W.  J.  Yoder, 
in  the  Journal  of  the  Western  Society  of  Engineers,  1897, 
gives  the  following  data:  The  tunnels  (built  in  1888-1889) 
are  within  the  northern  city  limits  of  Wheeling,  W.  Va.,  and 
the  material  penetrated  was  for  the  most  part  shale  of  the 
coal  measures.  The  shale  disintegrates  rapidly  upon  ex- 
posure and  must  be  supported.  The  block  or  American 
system  of  timbering  was  used  for  lining,  and  was  kept  never 
more  than  50  ft.  back  of  the  face.  All  drilling  was  done  by 
hand,  and  the  position  of  drill  holes  is  shown  by  sketches  in 
the  article.  A  top  heading  10  x  34  ft.  was  driven,  and  then 
widened;  the  bench  was  taken  out  in  two  lifts.  The  first 
or  cut  holes  in  the  heading  were  drilled  so  as  to  blast  out  a 
long  horizontal  wedge  of  rock  near  the  roof;  these  holes 
being  5  to  6  ft.  deep.  Then  a  lower  row  of  5-ft.  lift  holes 
was  fired.  Finally  the  bottom  of  the  heading  was  taken 
out  like  a  bench  by  a  row  of  vertical  holes  and  a  row  of 
horizontal  holes.  In  all  33  holes  were  fired  in  the  heading, 
aggregating  160  lin.  ft.,  and  requiring  60  Ibs.  of  40  per  cent. 
Forcite  to  load  them.  The  effect  of  the  firing  was  to  make 
an  advance  of  2^2  ft.,  displacing  25  cu.  yds.  The  heading 
gang  consisted  of  i  foreman,  14  drillers,  12  muckers  and  I 
nipper.  About  25  lin.  ft.  of  drilling  was  considered  a  day's 
(10  hrs.)  work  for  2  men.  The  muck  was  wheeled  in  iron 
barrows  to  a  traveler  and  dumped  down  chutes  into  cars. 
The  heading  gang  timbered  and  placed  the  packing  above 
the  arch;  two  lo-hr.  shifts  per  week  being  needed  for  this 
work,  leaving  10  shifts  per  week  for  advancing  the  head- 
ing. The  timbering  is  fully  described ;  660  ft.  B.  M.  of  white 
oak  were  used  per  lin.  ft.  of  tunnel.  The  bench  holes  were 
8  ft.  deep,  churn  drills  being  used  except  for  the  corner  holes 
and  for  blockholing.  The  bench  force  consisted  of  I  fore- 
man, 6  drillers,  18  muckers,  2  mule  drivers,  3  dump  men 
and  i  nipper.  The  average  haul  was  about  800  ft. 


314        ROCK  EXCAVATION— METHODS  AND  COST. 

The  maximum  monthly  progress  (working  two  lo-hr. 
shifts)  in  a  heading  on  the  Mount  Wood  Tunnel  was  130 
lin.  ft.,  the  average  monthly  progress  being  84  ft.  The  maxi- 
mum monthly  progress  on  the  bench  was  125^  ft.,  the  aver- 
age being  97  ft.  The  average  excavation  was  10.2  cu.  yds, 
per  lin.  ft.  of  heading  and  enlargement,  and  18  cu.  yds.  per 
lin.  ft.  of  bench.  The  total  excavation  in  both  tunnels  was 
49,670  cu.  yds.,  and  the  excavation  in  approaches  was  25,751 
cu.  yds. 

The  number  of  men  employed  was  350.  The  heading  men 
were  composed  of  two-thirds  Negroes  and  one-third  Aus- 
trians.  The  foremen  were  Irish.  The  best  drillers  were 
Negroes.  No  work  was  done  Sundays  or  Saturday  nights. 
The  scale  of  wages  (lo-hr.  shift)  was  as  follows: 

Heading  Gang. 

i  foreman  at  $4.00 

14  drillers  "      1.75 

10  muckers  1.50 

i  nipper  "       1.25 

Bench  Gang. 

1  foreman  at    $3.00 
6  drillers  "      1.75 

16  muckers  "       1.50 

2  men  (lagging)  "      1.50 

1  nipper  "      1.25 

2  drivers  "      1.50 

3  dumpmen  "      1.50 

2  mules 

Miscellaneous, 

i  carpenter                     at  $2.50 

4  sawyers                        "  1.75 
i  trackman                     "  2.50 

3  blacksmiths                  "  3.00 
i  walking  boss                 "  4.00 
i  timekeeper                    "  2.25 
i  engineer  and  fireman  "  2.50 
i  electrician                     "  2.50 


COST  OF  RAILWAY   TUNNELS.  315 

Cost  of  Labor  per  Lin.  Ft.  of  Tunnel. 
Labor  excavating  (heading,  $22.79;  bench,  $20.95)  .  .$4374 

Hauling  and  dumping 5-^5 

Labor  timbering 4.19 

"      framing  timber 77 

Blacksmithing i.oo 

Track  repairs 21 

Labor  electric  lighting 88 

Superintendance  and  accounts 2.00 


Total  labor  $58-44 

Cost  per  cu.  yd 2.06 

The  above  does  not  include  the  cost  of  timber,  oil,  fuel, 
wear  of  tools  or  explosives.  About  I  Ib.  of  40  per  cent. 
Forcite  was  used  per  cu.  yd.  of  tunnel  excavation,  or  28  Ibs. 
per  lin.  ft.  The  labor  cost  was  $2.34  per  cu.  yd.  of  heading, 
and  $1.10  per  cu.  yd.  of  bench  excavation,  making  an  aver- 
age of  $1.55  per  cu.  yd.,  not  including  the  items  of  timber- 
ing, etc.  The  labor  cost  of  erecting  arch  and  packing  back 
of  it  was  $3.19  per  lin.  ft.  of  tunnel;  or  $7.80  per  1,000  ft. 
B.  M.  The  labor  cost  of  erecting  plumb  posts  and  side  lag- 
ging and  packing  same  was  $2.33  per  lin.  ft. ;  or  $4.27  per 
i  ,000  ft.  B.  M.  The  contractors  were  Paige,  Carey  &  Co., 
of  New  York,  whose  superintendent  was  Mr.  Frank  Moran. 

Tunnel  Driven  by  Hand  on  the  B.  &  0. — In  Engineering 
News,  April  5,  1894,  Mr.  J.  G.  G.  Kerry  gives  description 
and  cost  of  a  short  tunnel  built  in  1891  on  the  W.  Va.  &  P. 
R.  R.,  a  feeder  of  the  B.  &  O.  system.  The  tunnel  is  on  a 
Y$  per  cent,  grade  falling  to  the  south,  with  a  length  of  624 
ft.,  in  a  soft  blue  clay  shale,  nearly  dry  and  showing  little 
stratification.  This  shale  disintegrates  rapidly  on  exposure. 
The  width  was  23  ft.,  height  from  floor  to  spring  line  13  ft. ; 
semi-circular  arch  of  11^2  ft.  radius.  The  area  of  the  head- 
ing was  208  sq.  ft. ;  bench,  299  sq.  ft. ;  total,  507  sq.  ft.  Work 
was  all  done  by  hand.  The  heading  gang  consisted  of  I 
foreman,  8  miners,  6  muckers  and  I  nipper.  Common  labor 


3i6        ROCK  EXCAVATION— METHODS  AND  COST. 

ers  were  paid  $1.45  and  miners  $1.75  per  ic-hr.  day.  Three 
sets  of  holes  (2  wet  and  I  dry)  were  drilled  in  the  heading; 
each  set  consisting  of  4  holes  about  4  ft.  deep ;  and  24  ft.  of 
hole  was  considered  a  good  day's  work  for  two  miners. 
Each  hole  was  loaded  with  4  to  6  sticks  (1/3  Ib.  per  stick) 
of  dynamite;  and  the  average  advance  from  a  blast  was  2l/2 
ft.  A  scaffold  car,  or  go-devil,  was  used  in  handling  the 
muck.  It  was  provided  with  a  derrick  and  also  used  for 
handling  timbers,  lagging  and  packing. 

The  bench  gang  consisted  of  I  foreman,  8  drillers,  10 
muckers  and  I  nipper.  The  bench  was  shot  down  in  4- ft. 
holds  or  lifts,  two  half-depth  blasts  being  made  for  each 
hold.  Each  blast  consisted  of  four  holes,  two  being  center 
holes,  and  two  nearly  vertical  under  the  wall  plate.  The 
charge  was  10  sticks  to  an  outside  hole  and  15  sticks  to  a 
center  hole.  Muck  was  taken  out  in  i  cu.  yd.  dump  cars  in 
trains  of  two.  Stone  flat  cars  with  platforms  flush  with  top 
of  wheels  were  used  for  handling  large  rocks.  The  bench 
was  kept  two  wall  plate  lengths  behind  the  heading,  making 
the  same  progress,  2^2  ft.  per  shift.  The  actual  excavation 
was  at  the  rate  of  5  ft.  per  shift,  but  the  time  consumed  in 
pointing  down  projections,  timbering  and  packing  being 
equal  to  the  time  spent  in  excavation,  reduced  the  average 
progress  to  2l/2  ft.  per  shift.  The  work  was  done  by  con- 
tract, and  it  cost  the  company  at  contract  prices  as  follows : 

11,726  cu.  yds.  of  excavation  at  $2.85 $33,419 

742  "      "       "packing       "      1.75 1,298 

256  "      "      "   fallen  rock  "      1.25 320 

303,000  ft.  B.  M.  "  30.00 9,090 


Total  624  lin.  ft.  of  tunnel  at  $70.70 $44,127 

The  actual  cost  to  the  contractor  was  about  $35,000. 

The  method  of  handling  and  placing  the  segmental  arch 

timbering  is  described  in  detail.    The  timbering  consisted  of 

a  7-segment  arch  of  12  x  12-in.  white  oak  resting  on  12  x  14- 

in.  wall  plates  on  top  of  the  posts.     The  i6-ft.  wall  plates 


COST  OF  RAILWAY   TUNNELS.  317 

were  jointed  by  halving  for  a  foot  at  each  end,  so  that  the 
forward  end  always  showed  the  lower  half  of  the  joint.  The 
arches  were  8  ft.  c.  to  c.  The  segments  of  the  arches  were 
erected  on  temporary  centers  made  of  2-in.  plank.  These 
centers  were  erected  in  two  parts  and  joined  at  the  crown  by 
bolts;  a  long  dog-hook,  fastened  to  the  center,  was  driven 
into  the  preceding  arch  to  hold  it  in  place  laterally.  The 
arch  timbers  were  wedged  solidly  against  the  roof,  and  the 
centers  withdrawn.  The  lagging  was  close  laid,  all  voids 
being  packed  with  broken  sandstone. 

Each  end  of  the  tunnel  was  lined  with  masonry  for  50  ft., 
the  centers  used  in  this  lining  being  25  ft.  long  and  mounted 
on  rollers.  During  use  the  centers  were  supported  on 
wedges,  which  upon  being  struck  lowered  the  center  enough 
to  clear  the  rock-faced  voussoirs.  A  hole  was  left  in  the 
crown  of  the  arch-center  lagging  so  that  the  voussoirs  could 
pass  through.  Above  this  a  piece  or  two  of  the  tunnel  lag- 
ging was  removed,  and  an  iron  bar  placed  on  the  timber 
arches.  A  set  of  blocks  was  hung  from  this  iron  bar,  and 
used  to  raise  the  voussoir  stone.  Gas  pipe  rollers  were  put 
under  the  stone  to  roll  it  to  place  on  the  center  lagging.  The 
stone  was  then  canted  up,  and  a  rope  slung  around  it,  six 
men  then  sliding  it  to  place. 

The  contract  prices  were  $9  per  cu.  yd.  for  portal  masonry, 
$8  for  side  walls  and  $14  for  arch  sheeting.  The  cost  at 
contract  prices  per  lin.  ft.  of  that  part  of  the  tunnel  which 
was  lined  (excluding  portals,  fallen  material,  etc.)  was: 

Excavation $53-55 

Packing 2.08 

Timbering 14.75 

Side  walls 20.56 

Arch 21.42 

Packing 2.08 


Total  per  lin.  ft $i  14.44. 


318        ROCK  EXCAVATION— METHODS  AND  COST. 

New  Croton  Tunnel. — In  Trans.  Am.  Inst.  Min.  Eng., 
Sept.,  1890,  Mr.  J.  P.  Carson  gives  the  following  data: 
Work  was  begun  in  1885  on  the  New  Croton  Aqueduct 
Tunnel,  which  was  nearly  as  large  as  a  single  track  railway 
tunnel.  The  following  were  the  areas  of  the  excavation : 

As  shown  Actual 

on  plans.  excavation. 

Area  above  the  spring  line  ....   73  sq.  ft.  105  sq.  ft. 

Area  below    "       "         "     ....131  "    "  178  "     " 

Total  area 204  "    "  283  "     " 

The  tunnel  was  lined  with  masonry  so  as  to  have  an  in- 
side width  at  the  spring  line  of  14  ft.  and  a  height  of  14  ft. 
The  contract  price  was  $7  per  cu.  yd.  of  excavation,  or 
$52.88  per  lin.  ft.  A  top  heading  8  x  16  ft.  to  9  x  17  ft.  was 
run  by  the  American  center  cut  system  of  drilling.  Several 
shafts  were  sunk  and  the  tunnel  driven  from  them.  Sinking 
shaft  I3A  a  distance  of  no  ft.  in  wet,  soft  material  cost 
$416  per  ft.  Cars  holding  I  cu.  yd.  of  broken  stone,  or  y*. 
cu.  yd.  of  solid  stone,  were  hauled  in  trains  of  2  or  3  cars 
by  one  mule.  Experiments  were  tried  to  determine  the  rela- 
tive advantage  of  driving  the  heading  and  bench  separately 
as  compared  with  driving  them  as  is  usual,  at  the  same  time, 
and  about  60  ft.  apart.  It  was  found  that  in  mica-schist 
when  the  heading  and  bench  were  driven  together  the  aver- 
age progress  of  completed  tunnel  excavation  was  30  ft.  a 
week  from  one  face.  The  average  weekly  progress  of  com- 
pleted tunnel  excavation  was  only  20.4  ft.  per  week  when  the 
heading  was  first  driven  through  to  the  next  shaft,  and  then 
followed  by  the  bench,  which  was  driven  through  separately. 
Out  of  76,490  ft.  of  tunneling  23  per  cent,  was  driven  by 
working  the  heading  and  the  bench  separately,  causing  a 
very  material  delay  in  completing  the  tunnel. 

Average  Weekly  Progress  in  Division  3. 


Mica-schist* 

Total  No.  of  Weeks. 

4.27 

Lin.  Ft. 
per  Week. 
-^0.0* 

Area. 
Sq.  Ft. 
28^ 

•*r"v 

*  Heading  and  bench  driven  at  the  same  time. 


COST  OF  RAILWAY   TV  I 
Limestone*   95  /^ 

VNELS. 

22.4* 
9.8* 

4.25* 
1.40* 

319 

283 
361 
490 
508 

Decomposed   rock*          152 

Sand  and  boulders*               .  .   62  x/3 

Soft  ground,  clay,  sand,  mica*  128 

Mica-schistf  

.  .47.of 

165 
105 
105 

Limestone*}*   

:.33.8f 

Decomposed  rock*j*               

.  .2^.t;t 

Mica-schist*j;  

.  .  s6.o± 

178 
178 
196 

Limestone"J!   

.  .27.O± 

Decomposed  rocki         , 

.I2.lt 

It  is  interesting,  to  note  that  although  faster  heading  prog- 
ress was  secured  by  driving  the  heading  clear  through  be- 
fore beginning  the  bench,  the  progress  was  not  enough  fast- 
er to  make  up  for  the  delay  in  waiting  to  begin  the  bench ; 
so  that  in  mica-schist  the  average  progress  per  week  of  head- 
ing and  bench  was  (47  +  36)  -"-  2  =  41^  ft.,  and  as  they 
were  worked  separately  the  final  average  of  completed  tun- 
nel was  41^2  -T-  2  =  20.7  ft.  per  week. 

The  men  decided  to  break  the  record  for  a  week's  run  in 
the  South  heading  from  Shaft  15,  beginning  at  a  point  3,200 
ft.  from  foot  of  shaft.  The  heading  was  9  x  17  ft.  in  gneiss. 
Plant:  I  duplex  Rand  compressor,  class  "B,"  rated  at  1,325 
cu.  ft.  per  min.,  at  80  Ibs.  pressure ;  4  and  5-in.  air  pipe ;  loss 
of  pressure  by  friction  in  3,400  ft.  of  pipe  was  15  Ibs.;  3 
slugger  drills ;  one  lo-hr.  shift  per  day : 

7  to  9:30  A.  M.  Mucking 2^2  hrs. 

9:30  A.  M.  to  4:30  P.  M.     Drilling 6 

4  '3°  to  5  Charging */2    " 

5  to  6  Firing i 

Total    10 

*  Heading  and  bench  driven  at  the  same  time. 

t  Heading  driven  alone. 

j  Bench  driven  alone  after  completing  heading. 


320        ROCK  EXCAVATION— METHODS  AND  COST. 

Distance  of  heading  run  in  a  week,  102  ft.  (best  previous, 
90  ft.)  ;  area,  145.5  S(l-  ft-  5  total,  550  cu.  yds. ;  25  per  cent,  of 
the  muck  left  in  tunnel 

8  center-cut  holes,  10  ft.  each 80  ft. 

12  side        "       "         8    "     "    96  " 


Total  ft.  drilled  per  shift 176 

Total  ft.  drilled  2,288,  or  4.16  ft.  of  hole  per  cu.  yd.  Total 
powder,  2,200  Ibs.,  4  Ibs.  per  cu.  yd.,  or  8.46  Ibs.  per  hole; 
13  blasts  fired  with  average  advance  of  7.86  ft.  Crew :  I 
heading  boss  at  $3.25  ;  3  drillers  at  $2.50;  3  helpers  at  $1.75  ; 
i  nipper  at  $i ;  I  powder  man  at  $i ;  I  muck  boss  at  $2.50;  9 
muckers  at  $1.50;  3  drivers  and  mules  at  $2.25;  i  trackman 
at  $1.50;  2  sumpmen  at  75  cts.  Outside  labor:  2  bellmen 
at  75  cts. ;  2  topmen  at  75  cts.  Power,  etc. :  i  engineer  at 
$15  a  week;  I  engine  driver,  $9;  i  fireman,  $12.25;  i  elec- 
trician, half  week,  $6;  I  machinist  (half  week),  $7;  I  car- 
penter (half  week),  $7.50;  i  blacksmith,  $15;  i  blacksmith 
helper,  $10;  i  time  keeper,  $14;  i  general  foreman,  $35. 
Record  Run  South  Headi-ng. 

Cu.  yd. 

Drill  crew $0.42 

Muck  crew 50 

Transporting 31 

Outside  labor 09 

Enginemen,  etc 18 

General  foreman .06 


Total  labor  $1.56 

5  tons  coal  at  $5  (7  days),  $175; 

Oil  and  candles,  $12.50;  steel,  $5 35 

2,200  Ibs.  rackarock  at  i6l/2  cts 65 

Total $2.56 

Interest  on  plant .37* 


$2.93 


Too  low. 


COST  OF  RAILWAY   TUNNELS.  321 

The  record  week's  run  on  North  Heading,  Shaft  16  (head- 
ing 9  x  1 6  ft.),  with  plant  same  as  above,  but  better  over- 
hauled, was  as  follows:  Work  was  pushed  to  the  utmost 
for  7  days  in  mica-schist ;  lo-hr.  shifts.  In  10  previous  weeks 
the  average  had  been  46.9  ft.  per  week.  This  week's  record 
was  127  ft.;  area,  125.6  sq.  ft.;  591  cu.  yds.;  15  to  20  per 
cent,  of  muck  left  in  tunnel.  Distance  from  compressor, 
3,965  ft. ;  loss  of  pressure,  20  Ibs. ;  2  Rattler  drills. 

8  center-cut  holes,  8^  ft.  each    68  ft. 

10  side       "       "      8       "       "   .  .  80  " 


Total 148  " 

Total:  1 8  shots;  324  holes;  2,664  ft-  drilled;  or  4.33  ft. 
per  cu.  yd. ;  2,050  Ibs.  60  per  cent,  powder ;  or  3.46  Ibs.  per 
cu.  yd. ;  or  6.33  Ibs.  per  hole ;  advance,  7.05  ft.  per  shot. 

Mucking 2.3  hrs. 

Drilling 5.5    " 

Charging 0.5 

Firing i.i    " 

Clearing  of  smoke   0.6    " 


Other  Examples  of  Rapid  Heading 

Work. 

Lin.  ft.  per 

No.  of 

Size  of 

3.             day   (lohrs.) 

Drills. 

Heading 

10.52 

4 

14x14 

10.21 

4 

ft 

/£                   11.75 

2 

8x  16 

10.05 

3 

" 

12.  l6 

3 

" 

15.07* 

3 

9x17 

Days. 
22 

26 


54 
60 

7 

60  7.81  9x16 

7  18.14*  2  9x16 

Rapid  bench  work:     In  84  days,  with  2  drills,  averaged 
6.85  lin.  ft.  per  day ;  3,360  cu.  yds. ;  4  holes  averaging  9  ft. 

*  Above  given  in  detail. 


322        ROCK  EXCAVATION— METHODS  AND  COST. 

deep  per  blast;  4,788  ft.  drilled;  1.4  ft.  per  cu.  yd.;  7,500 
Ibs.  powder,  or  2.23  per  cu.  yd. ;  bench  worked  at  both  ends. 
The  above  are  record  costs.    The  following  are  average 
costs,  and  are  double  the  costs  on  the  record  runs : 

Heading,  area  105  sq.  ft.  Cu.  yd. 

Inside  labor $3-34 

Outside  labor 94 

Coal  (3  tons  day)   67 

Powder  at  i6l/2   50 

Interest  on  plant 37* 


$5.82 

By  driving  two  headings  at  one  time,  outside 
labor  cut  in  two  saving  .................  50 


Average  cost  of  bench  excavation  :  Area,  167.4  sq.  ft.  ;  577 
lin.  ft.  in  48  days  (two  lo-hr.  shifts  per  day)  ;  3,578  cu.  yds.  ; 
I  drill  boss,  $70  per  mo.  ;  i  muck  boss,  $70  per  mo.  ;  I  drill 
runner,  $2.50;   i   drill  helper,  $2;  15  muckers  at  $1.50;   I 
driver  and  mule,  $2.25;  i  trackman,  $1.50;  2  dumpmen  at 
$1.50;  i  bellman,  $1.75  ;  i  sumpman,  $1.75  ;  i  topman,  $1.50  ; 
outside  labor  as  above  given. 

Cu.  yd. 
Drilling  and  blasting  (532  holes,  9  ft.)    .  .    .  .$0.28 

Mucking  (3,360  cu.  yds.)    .................  75 

Transporting  ............................  20 

Outside  labor  at  shaft  .....................  17 

Extra          "      "      "      .....................  05 

Enginemen,    etc  ..........................  17 

Machinist,  blacksmith  and  helper  ...........  09 

Coal  (3  tons,  at  $5  ;   oil  and   candles,    at   $2 
per  day)    .............................     .23 

Powder   (7,300  Ibs.  J.  L.  Aqueduct  at   i6y2 
cts.),  etc  ...............................  38 

*  Too  low  an  estimate. 


COST  OF  RAILWAY  TUNNELS.  323 

Interest  on  plant   $°-37* 

Total  cost  per  cu.  yd.  of  bench $2.69 

Cost  of  driving,  heading  and  bench  together:  30  lin.  ft.; 
area,  283  sq.  ft. ;  314  cu.  yds. : 

Cu.  yd. 

Inside  labor  on  heading  120  c.  y.  at  $3.34  )        <* 
"       "  bench      194  c.  y.  at  $1.23  f  ' 

Outside  labor 78 

Coal,  etc 62 

Powder  (3  Ibs.  per  c.  y.  of  heading;  2.3  Ibs. 
per  c.  y.  of  bench,  at  16^2  cts.) 44 


Total  for  single  heading  and  bench $ 

The  Cascade  Tunnel. — This*  tunnel  is  described  in  En- 
gineering News,  Jan.  10,  1901,  by  Mr.  John  F.  Stevens,  Chief 
Engineer,  Great  Northern  Railway.  The  tunnel  is  13,813  ft. 
long  through  the  Cascade  Mts.  on  the  line  of  the  Great 
Northern  Ry.  The  width  in  the  clear  is  16  ft.,  and  the  height 
from  top  of  rail  to  bottom  of  arch  is  21%  ft.  It  was  begun, 
from  two  headings,  Aug.  20,  1897,  and  completed  Oct.  13, 
1900.  A  top  heading,  10  x  20  ft.,  was  driven  from  each 
end ;  and  the  bench  was  taken  out  in  two  lifts.  The  average 
monthly  progress  was  175  ft.  at  each  heading,  or  5.76  ft. 
per  day  of  24  hours.  The  best  year's  work  was  from  June 
i,  1899,  to  June  i,  1900,  in  which  time  5,575  ft.  were  driven 
from  the  two  headings,  the  monthly  average  being  232  ft. 
per  heading.  The  best  month's  progress  was  527  ft.  from 
two  headings ;  the  best  week's  progress  was  143  ft.  from 
two  headings ;  the  best  month's  progress  from  a  single  head- 
ing (East)  was  301  ft.  The  rock  was  medium  hard  granite, 
very  seamy  and  very  wet.  Although  hard  to  drill  and  blast, 
the  granite  disintegrated  so  rapidly  that  a  temporary  timber 
lining  was  necessary  throughout,  and  it  was  afterward  re- 
placed with  concrete. 

*  Too  low. 

t  Deduct  $0.70  reduced  fixed  charges  when  two  headings  are  run. 


324        ROCK  EXCAVATION— METHODS  AND  COST. 

The  work  was  all  done  by  day  labor,  no  contracts  being 
let.  Three  8-hr,  shifts  were  worked.  There  were  600  to 
800  men  employed,  and  they  were  not  very  efficient. 

Four  columns  in  a  heading  carried  6  drills  ($%-m.  size). 
From  24  to  28  holes  were  drilled  12  ft.  in  the  heading,  and 
fired  in  three  rounds  by  electricity.  Including  the  bench 
work  there  were  14  drills  used  at  each  end  of  the  tunnel. 
Rock  from  the  heading  and  top  bench  was  wheeled  in  bar- 
rows out  onto  the  "jumbo,"  or  "go  devil,"  and  dumped 
through  into  cars  below.  A  compressed  air  hoist  on  the 
"jumbo"  served  to  lift  large  rock  and  to  shift  the  "jumbo" 
back  before  firing.  Eight  electric  motor  cars  were  used  to 
haul  the  muck,  etc.  One  motor  hauled  16  to  20  dump  cars 
of  i  cu.  yd.  each  up  the  1.7  per  cent,  grade  to  the  east  portal, 
at  10  miles  an  hour.  The  rails  were  5<>lb.  rails  laid  to  a 
gage  of  2  ft. 

Large  power  houses  were  built  at  each  portal.  The  east 
power  house  contained  one  Ingersoll-Sergeant  duplex  com- 
pressor, 1 8  x  24  ins. ;  one  straight  line  compressor,  18  x  24 
ins. ;  one  Rand  duplex  compressor,  20  x  36  ins. ;  one  Buckeye 
high-speed  engine,  12  x  16  ins. ;  one  Chandler  &  Taylor 
high-speed  engine,  13  x  14  ins.;  six  I5O-H.-P.  boilers; 
pumps,  dynamos,  fans  and  water  heaters.  Compressed  air 
was  delivered  through  6-in.  mains  to  the  drills,  at  an  initial 
pressure  of  100  Ibs. 

The  tunnel  was  lined  with  concrete  from  end  to  end,  the 
temporary  timber  lining  being  removed.  The  concrete  is 
nowhere  less  than  2  ft.,  and  in  places  it  is  3^  ft.  thick; 
spawls  and  broken  stone  were  packed  above  the  concrete 
where  necessary.  To  place  the  concrete  without  interfering 
with  the  muck  trains,  a  platform  500  ft.  long  was  erected, 
and  the  cars  loaded  with  concrete  were  hauled  up  an  incline 
by  a  compressed  air  hoist.  The  concrete  was  dumped  on 
the  platform  and  shoveled  into  the  forms.  While  this  was 
going  on  another  5oo-ft.  platform  was  being  built  in  ad- 
vance. Side  walls  were  built  in  alternate  sections  8  to  12  ft. 


COST  OF  RAILWAY  TUNNELS.  325 

long,  the  weight  of  the  timber  arches  being  thus  transferred 
to  the  walls.  The  concrete  arch  centers  were  made  in  12-ft. 
lengths,  of  which  there  were  ten  in  each  end  of  the  tunnel. 
When  the  concrete  had  set  the  12-ft.  arch  center  was  lowered 
with  screw  jacks  onto  "dollies,"  pushed  forward  12  ft.  and 
jacked  up  again.  Concrete  was  mixed,  I  cement,  3  sand  and 
5  parts  rock.  About  95,000  barrels  of  Portland  cement  were 
used  in  lining  the  tunnel,  an  average  of  7  bbls.  per  lin.  ft.  of 
tunnel.  Work  of  lining  was  begun  in  Dec.,  1899,  and  fin- 
ished Nov.,  1900;  more  than  1,000  ft.  of  lining  having  been 
placed  in  Oct.,  1900,  in  the  west  end,  although  the  general 
average  was  about  600  ft.  of  lining  per  month  from  each 
end.  The  tunnel  was  opened  for  operation  Dec.  20,  1900. 

Mr.  Willard  Beahan,  in  a  letter  to  Engineering  News, 
Feb.  28,  1901,  adds  some  interesting  facts  about  the  part  of 
the  tunnel  driven  through  soft  ground,  at  the  start,  where 
only  0.8  ft.  per  day  was  averaged.  He  also  says  that  it  was 
a  serious  mistake  to  have  driven  the  heading  in  rock  by 
hand  300  ft.  in  advance  of  the  bench  while  waiting  for  the 
power  plant  to  arrive,  for  the  long  heading  overtaxed  the 
transportation  so  that  work  on  the  heading  had  to  be  stopped 
until  the  bench  was  brought  up.  The  use  of  four  drill 
columns  he  regards  as  novel,  and  adds  that  there  was  plenty 
of  room  in  which  to  work  six  drills,  and  that  it  was  not  nec- 
essary to  shift  any  of  the  columns  in  drilling  a  set  of  holes. 

The  Kellogg  Tunnel. — Mr.  U.  B.  Hough,  in  Engineering 
News,  April  25,  1901,  describes  a  novel  method  of  mucking 
used  in  running  a  large  tunnel  in  the  Bunker  Hill  and  Sul- 
livan mines,  at  Kellogg,  Idaho.  The  entire  length  of  the 
tunnel  will  be  9,000  ft.,  of  which  8,400  ft.  had  been  driven 
at  the  time  of  writing.  The  rock  is  quartzite  and  after 
blasting  is  loaded  by  a  No.  I  drag-scraper,  which  is  hauled 
up  an  incline  by  a  hoisting  engine,  and  dumped  through  a 
door  into  the  car.  Two  scraper  loads  usually  fill  a  i-cu.-yd. 
car,  and  never  more  than  three  loads.  After  the  first  car 
is  loaded,  the  second  car  is  pulled  forward  under  the  door. 


326        ROCK  EXCAVATION— METHODS  AND  COST. 

Five  men  constitute  the  mucking  gang,  one  operating  the 
hoist,  one  attending  the  cars  and  three  loading  and  attending 
the  scraper.  The  time  required  to  remove  40  to  50  cu.  yds. 
of  waste  is  2  to  2^/2  hrs.  (not  stated  whether  the  yardage 
is  solid  or  loose  measure).  The  incline,  or  "mucker,"  is 
moved  by  jacking  it  up  (on  four  screw  jacks)  off  the  floor 
until  the  weight  is  on  the  moving  car ;  it  is  pushed  back  until 
advance  rails  are  laid,  then  it  is  pushed  forward  and  lowered 
to  the  floor  again.  The  hoist  is  moved  in  a  similar  manner 
by  running  a  moving  car  under  it.  Five  men  consume  only 
20  mins.  in  moving  both  hoist  and  mucker.  The  mucker 
has  been  in  use  15  mos.,  and  is  in  fair  condition.  Two  drills 
mounted  on  one  bar  are  worked  in  the  heading,  which  is 
kept  10  to  20  ft.  in  advance  of  the  bench.  A  four-ton  elec- 
tric motor  hauls  a  train  of  15  loaded  cars.  Smoke  is  re- 
moved through  a  22-in.  pipe  (No.  18  iron)  by  a  No.  9 
Sturtevant  exhaust  fan.  This  fan.  will  remove  all  smoke  in 
15  or  20  mins.  through  8,000  ft.  of  pipe.  The  longitudinal 
pipe  seams  are  all  riveted  and  soldered;  and  the  joints  are 
wrapped  with  sheeting  and  painted  with  tar.  In  the  month 
of  October,  1898,  an  advance  of  354  ft.  was  made,  but  the 
general  average  has  been  7.5  ft.  per  day,  working  three  8- 
hr.  shifts.  One-third  of  the  tunnel  has  been  timbered. 

The  Pryor  Gap  Tunnel. — Mr.  F.  T.  Darrow  describes  this 
tunnel  in  Engineering  News,  July  3,  1902.  The  tunnel  is 
single  track,  on  the  line  of  the  "Burlington"  in  Montana, 
38  miles  south  of  Billings.  It  is  500  ft.  long,  on  a  curve, 
through  solid  dolomitic  limestone.  The  tunnel  section  out- 
side of  the  timbering  runs  18  cu.  yds.  per  lin.  ft.,  and  was 
taken  out  by  a  top  heading  and  two  benches,  each  about  9  ft. 
high.  The  work  was  done  by  contract,  actual  tunnel  work 
beginning  December,  1900.  A  I6-H.-P.  upright  boiler  fur- 
nished steam  to  two  3M$-in.  drills  in  the  heading  and  one 
drill  on  the  bench.  The  steam  was  carried  in  2-in.  and  \y2- 
in.  wrought  pipe  covered  with  jointed  jacketing;  and  at  a 
distance  of  400  ft.  from  the  boiler  no  difficulty  was  found 


COST  OF  RAILWAY   TUNNELS.  327 

in  running  the  drills.  Two  lo-hr.  shifts  were  worked  daily, 
or  13  shifts  a  week;  and,  when  running  well,  the  advance 
was  50  ft.  a  week  from  one  heading.  The  heading  gang 
consisted  of  I  foreman,  2  drillers,  2  helpers,  6  or  7  muckers, 
i  powderman,  beside  the  fireman  and  teamster  outside.  The 
bench  force  was  about  the  same,  excepting  that  there  was 
only  one  driller  and  helper.  In  heading  work  each  machine 
was  mounted  on  a  separate  column ;  and  a  set  of  14  holes  6 
ft.  deep  was  put  in  and  fired  in  four  rounds,  using  60  per 
cent,  dynamite.  The  south  heading  was  run  in  300  ft.,  and 
then  stopped,  and  the  bench  brought  up,  the  heading  gang 
moving  to  the  bench  at  the  north  end,  which  up  to  that  time 
had  been  run  without  bench  excavation.  The  work  was 
completed  May  15.  Forty  pounds  of  60  per  cent.  Giant 
and  10  Ibs.  of  black  powder  were  used  per  lin.  ft.,  the  black 
powder  being  used  only  in  the  bench.  Timbering  was  put 
in  after  the  completion  of  the  excavation  while  the  tunnel 
was  in  operation.  The  particular  feature  of  this  work  is 
the  simplicity  of  the  plant  and  the  effectiveness  of  the  small 
gang  of  men. 

The  Busk  Tunnel. — The  following  data  are  given  in  En- 
gineering News,  Sept.  27,  1894:  The  Busk  Tunnel  Ry.  Co. 
built  a  tunnel  9,395  ft.  long  on  the  Colorado  Midland  R.  R. 
through  the  Rocky  Mts.,  11.7  miles  S.  W.  of  Leadville.  The 
contract  was  let  to  Keefe  &  Co.,  and  work  was  begun  Sept. 
15,  1890.  After  all  but  921  ft.  had  been  driven  the  work 
was  turned  over  to  the  railway  company  and  finished  under 
the  direction  of  their  chief  engineer,  Mr.  B.  H.  Bryant. 
The  tunnel  is  single  track,  15  x  21  ft.,  with  10.2  cu.  yds. 
per  lin.  ft.  excavation  in  rock  and  13.8  cu.  yds.  where  tim- 
bered. The  heading  was  7  ft.  high  and  the  full  width  of 
the  tunnel.  The  first  8  holes,  8  ft.  deep,  were  drilled  in  two 
rows  from  top  to  bottom,  holes  being  about  2  ft.  apart  at 
surface  and  converging  toward  the  center.  The  firing  of 
these  holes  made  a  V-shaped  opening.  A  second  set  of 
holes  was  drilled  parallel  to  the  sides  of  the  tunnel,  and  when 


328        ROCK  EXCAVATION— METHODS  AND  COST. 

fired  the  remaining  rock  was  blown  into  the  V-shaped  open- 
ing. The  bench  was  excavated  in  the  same  way.  The  prog- 
ress was  as  follows : 

Driving  the  2  headings 1,118  days. 

Av.  daily  progress   8.4  ft. 

Av.  daily  progress,  best  month 10.9  " 

Best  month's  (28  days)  progress,  one 

heading 202.5  " 

The  rock  was  granite,  and  in  places  it  disintegrated  on 
exposure,  requiring  timbering;  in  other  places  it  was  so 
full  of  seams  as  to  require  timbering ;  so  that  78  per  cent,  of 
the  tunnel  was  timbered.  The  contractor  was  paid  for  the 
tunnel  as  follows : 

9,393  2/3  ft-  of  tunnel  at  $62.50 $587,10375 

32,575   cu.  yds.  enlargement  for  timbering  at  $2.50 81,437.50 

Cost  of  timber,  2,723,000  ft.  B.  M.  at  $30 81,690.00 

Labor  timbering  at  $12  per  M .     32,676.00 


Total  9,393  2/3   ft.   at   $82.30 $782,907.50 

The  plant  at  the  Invanhoe  end  consisted  of  three  100- 
H.-P.  boilers,  two  20  x  24-in.  Ingersoll  compressors,  one 
20  x  24-in.  Norwalk  compressor,  one  IO-H.-P.  engine  to 
drive  electric  light  dynamo,  one  2O-H.-P.  engine  to  drive  a 
No.  6  Blake  blower,  14-in.  air  pipe,  two  pumps  with  14-in. 
steam  cylinders  and  lo-in.  stroke,  six  3^ -in.  Ingersoll  drills 
(4  in  the  heading  and  2  on  the  bench),  a  small  traction 
engine  running  on  a  2O-in.  gauge  track  hauling  nine  3~yd. 
dump  cars.  Coke  was  used  as  fuel  for  the  traction  engine, 
so  that  the  smoke  did  not  inconvenience  the  tunnel  workmen. 

Sutro  Tunnel. — Drinker  gives  in  considerable  detail  the 
work  done  in  driving  the  heading  of  this  drainage  tunnel  in 
Nevada.  The  work  was  begun  in  1869  by  hand,  and  in  1874 
Burleigh  drills  were  introduced.  The  heading  was  8  x  10 
ft.,  with  cut  holes  7^  ft.  deep  and  4^  ft.  apart.  It  is  stated 
that  6  Burleigh  drills  were  operated,  but  if  so  they  must 
have  been  unusually  crowded.  There  were  12  men  oper- 


COST  OF  RAILWAY   TUNNELS.  329 

ating  these  drills  on  each  shift,  and  these  same  men  were 
required  to  do  their  own  mucking  besides.  Subsequently  4 
Ingersoll  drills  replaced  the  6  Burleighs.  The  rock  was  a 
hard  trachite  and  greenstone.  In  1875,  working  three  8-hr, 
shifts,  the  average  progress  of  the  heading  was  72  ft.  a  week, 
or  3.4  ft.  per  8-hr,  shift ;  and  the  best  month's  advance  was 
350  ft.  During  the  last  8  mos.  of  the  year  1875  the  ac^" 
vance  was  2,561  ft.,  which  required  9,882  holes  (2  to  2l/2- 
in.)  averaging  6.77  ft.  per  hole,  making  a  total  of  66,951  ft. 
of  hole  to  excavate  about  7,680  cu.  yds.,  or  8.7  ft.  of  hole 
per  cu.  yd.;  and  16,700  carloads  were  moved.  The  powder 
was  No.  i  giant  and  the  amount  used  was  2.62  Ibs.  per  hole, 
or  3  1/3  Ibs.  per  cu.  yd.  There  were  470  drills  sharpened 
per  week,  although  1,100  drills  were  sharpened  one  week 
when  in  very  hard  rock.  There  were  105  men  employed  in 
and  about  the  tunnel,  working  in  three  shifts.  In  1877  the 
best  month's  advance  was  388  ft.,  which  was  certainly  an  ex- 
cellent record. 

Musconetcong  Tunnel. — Drinker  describes  the  work  on 
this  tunnel  in  his  book,  also  in  Trans.  Am.  Inst.  Min.  Eng., 
1875.  The  tunnel  is  12  miles  from  Easton,  Pa.,  on  the  Le- 
high  Valley  R.  R.,  and  was  begun  in  1872.  The  material 
penetrated  was  3,731  ft.  of  very  hard  syenite  gneiss,  460 
ft.  of  limestone  and  770  ft.  of  earth.  One  shaft  was  sunk. 
Top  headings  8  x  26  ft.  were  first  started  by  hand  with  a 
progress  of  40  to  60  ft.  per  month.  Ingersoll  drills  were 
subsequently  installed  and  were  operated  on  two  carriages, 
each  supporting  three  drills.  The  cutholes  were  10^  ft. 
deep  and  started  9  ft.  apart;  the  other  holes  were  12  ft. 
deep,  starting  2^  ins.  diam.  and  ending  up  iy2  ins.  diam. 
The  12  cut  holes,  drilled  in  pairs,  were  loaded  with  25  Ibs. 
of  No.  I  dynamite  and  50  Ibs.  of  No.  2,  and  fired  by  elec- 
tricity. No.  2  was  used  entirely  in  the  squaring  up  holes. 
The  total  charge  in  the  heading  was  25  Ibs.  of  No.  I  and  245 
Ibs.  of  No.  2,  resulting  in  advance  of  10  ft.  for  408  ft.  of 
drill  holes.  About  6  ft.  of  hole  were  drilled  per  cu.  yd.,  and 


330        ROCK  EXC  Ay  AT  ION— METHODS  AND  COST. 

about  4  Ibs.  of  No.  2  and  0.4  Ib.  of  No.  I  were  used  per  cu. 
yd.  To  drill  these  408  ft.  of  holes  required  four  8-hr,  shifts 
of  six  drills  on  each  shift,  so  that  each  drill  averaged  only 
17  ft.  of  hole  per  8-hr,  shift!  The  crew  on  each  shift  con- 
sisted of  the  following  men,  and  I  have  assumed  wages  to 
be  as  given : 

6  drillers,      at  $3.00 $18.00 

6  helpers  2.00 12.00 

6  muckers     "      1.50 9.00 

i  nipper         "      1.50 1.50 

i  boss  "      3.50 3.50 


Total  per  shift  $44.00 

The  bench  was  12  ft.  high  and  a  row  of  four  12-ft.  ver- 
tical holes  was  drilled  9  ft.  back  from  the  face;  then  two 
more  12-ft.  vertical  holes  were  drilled  close  up  to  the  sides 
of  the  tunnel  and  4^  ft.  back  of  the  face ;  then  four  bottom, 
horizontal  holes,  10  ft.  deep,  were  drilled  into  the  face  close 
to  the  floor  of  the  tunnel.  These  10  holes  were  charged 
with  107  Ibs.  of  No.  2,  and  a  9-ft.  advance  was  made  by 
each  firing.  The  bench  was  kept  500  ft.  back  of  the  face, 
and  the  bench  crew  consisted  of  3  drillers,  3  helpers,  14 
muckers,  i  nipper  and  i  boss  for  each  shift. 

The  total  amount  of  explosives  used  in  excavating  82,000 
cu.  yds.  of  heading  and  bench  combined  was  0.34  Ibs.  No.  I 
plus  1.71  Ibs.  of  No.  2  per  cu.  yd.  of  tunnel  excavation,  I 
exploder  and  3  ft.  of  connecting  wire  per  cu.  yd. 

The  plant  consisted  of  30  drills,  4  compressors,  9  boilers, 
2  machine  shops,  il/2  miles  of  6-in.  air  and  water  pipe,  2 
hoisting  engines  and  boilers,  pumps,  etc.  The  coal  and  sup- 
plies were  hauled  one  mile  over  rough  roads  with  4-horse 
teams,  and  there  were  24  teams.  In  three  years  there  were 
27,000  tons  of  coal  used.  The  force  all  told  was  about  1,000 
men. 

A  Tunnel  Through  the  Palisades,  N.  J. — In  Engineering 
News,  March  30,  1893,  a  brief  description  is  given  of  a  tun- 


COST  OF  RAILWAY   TUNNELS.  33* 

nel  through  the  Palisades  in  N.  J.,  about  2  miles  north  of 
the  Weehawken  Tunnel  of  the  West  Shore  (see  Eng.  Neivs, 
June  17,  1882).  This  tunnel,  which  was  being  built  by  the 
Hudson  R.  R.  &  Terminal  Co.,  was  begun  Aug.  I,  1892,  and 
is  5,070  ft.  long,  through  trap  rock.  In  solid  rock  the 
section  is  27  ft.  wide  by  21  ft.  high,  the  roof  being  an 
ellipse  with  a  9~ft.  rise.  The  tunnel  is  driven  by  a  top  head- 
ing 7x18  ft.,  24  holes  8  ft.  long  being  drilled  in  the  face ; 
8  center-cut  holes  and  two  rounds  of  8  holes  each  are  fired 
in  three  blasts. 

Rand  and  Ingersoll  drills  with  2^2-in.  starting  bits  are 
used,  and  30  ft.  for  each  drill  in  a  lo-hr.  shift  is  considered 
good  work.  The  dynamite  is  60  per  cent.  A  derrick  car 
is  used  in  mucking  the  benches  which  break  out  heavy; 
this  car  lifts  the  body  of  a  mucking  car  from  the  track  along- 
side and  places  the  body  close  up  to  the  bench  to  be  filled. 
By  this  means  large  stones  can  be  rolled  into  the  car  body. 
Wheelbarrow  loads  from  the  heading  are  dumped  from 
staging  into  these  car  bodies.  The  derrick  car  also  handles 
heavy  stones. 

The  Tequixqueac  Tunnel. — In  Engineering  Record,  Feb. 
29,  1896,  an  abstract  is  given  of  an  article  in  Engineering  on 
the  Tequixqueac  Tunnel,  for  drainage  of  City  of  Mexico. 
The  tunnel  is  6%  miles  long  in  sandstone;  circular  cross- 
section,  14  ft.  diam.  inside  brick  lining.  The  shaft-sinking 
method  is  outlined.  Water  was  present  in  large  quantities. 
Tunnel  headings  were  6^4  ft.  high,  5  ft.  wide  at  bottom 
and  4  ft.  at  top,  inside  timbers,  with  a  water  ditch  3  ft.  deep. 
Six  holes  6^2  ft.  deep  were  drilled  in  the  face  and  loaded 
with  6  Ibs.  of  Nobel  dynamite.  Dynamite  cartridges  were 
dipped  in  grease.  Drills  were  put  into  the  holes  to  keep  the 
charge  down.  Each  blast  threw  down  8  cu.  yds.  of  rock 
upon  timber  platform.  Cars  held  12  cu.  ft.,  on  2-ft.  gage, 
12-lb.  rails  on  iron  ties,  in  2o-ft.  lengths.  No.  I  Root  blow- 
er, 6-in.  outlet,  forced  air  through  6-in.  spiral  pipe  to  within 
10  ft.  of  face,  which  was  always  sufficient  for  2,100  ft.  from 


332        ROCK  EXCAVATION— METHODS  AND  COST, 

shaft.  Men  worked  under  sub-contractor  in  4-hr,  shifts, 
then  rested  4  hrs. ;  then  worked  4  hrs.  more,  changing  fore- 
men every  shift,  which  proved  a  splendid  arrangement. 
There  were  60  men  on  a  heading  shift  thus :  2  timbermen,  4 
drillers,  2  mucking  debris,  22  loading  cars  and  running  them 
(2  pushing  a  car),  2  plate  layers,  4  men  timbering,  I  ven- 
tilator man,  10  men  digging  water  channel  with  bars,  i 
oiling  and  greasing,  2  hookers  on,  2  dumpmen,  overseers, 
foremen  and  timekeepers.  Each  contractor  was  required 
to  make  a  minimum  progress  in  driving  heading  of  26  ft. 
in  24  hrs.  As  an  actual  fact,  one  heading  was  driven  43^ 
ft.  in  24  hrs.,  and  728  ft.  were  driven  in  a  month !  So  far 
as  I  know  this  record  has  never  been  equaled.  It  is  stated 
that  the  organization  of  the  forces  was  perfect,  and  that  the 
working  of  4-hr,  shifts  was  a  pronounced  advantage,  as 
the  men  worked  with  great  energy  even  in  very  wet  head- 
ings. It  will  be  noted  that  each  hand  driller  averaged  not 
less  than  13  ft.  of  hole  (two  6^-ft.  holes)  in  8  hrs.  It  is 
not  clear  how  22  men  could  have  been  employed  in  so  nar- 
row a  heading  loading  cars  and  tramming;  certainly  their 
yardage  output  per  man  was  nothing  remarkable,  except  for 
its  lowness. 

The  Simplon  Tunnel. — Americans  may  well  study  the 
methods  by  which  this  tunnel  has  been  driven ;  for  to  have 
maintained  a  rate  of  speed  practically  double  the  rate  usu- 
ally made  in  good  ground  in  this  country  is,  of  itself,  suffi- 
cient to  rivet  the  attention.  In  Engineering  News,  Aug.  30, 
1900,  is  printed  a  valuable  paper  on  this  tunnel,  by  Mr.  C. 
B.  Fox,  from  which  the  following  data  have  been  abstracted : 
The  Simplon  Tunnel  pierces  the  Alps  between  Italy  and 
Switzerland,  and  its  length  when  completed  will  be  64,725 
ft,  or  nearly  n  miles.  It  will  be  completed  in  1904.  One 
full' sized  railway  tunnel  (No.  i)  is  being  driven,  and  the 
heading  of  what  will  eventually  be  another  tunnel  (No.  2) 
is  also  being  driven  parallel  with  the  main  tunnel ;  the  two 
headings  being  56  ft.  apart  c.  to  c.  The' headings  are  bottom 


COST  OF  RAILWAY   TUNNELS.  333 

headings.  Cross-headings  connect  the  two,  every  660  ft. 
The  material  is  all  carried  to  the  portals,  there  being  no 
shafts.  The  cross-section  of  tunnel  No.  i  is  13.6  ft.  at  the 
formation  level,  increasing  to  16.4  ft.,  with  a  total  height 
of  18  ft.  above  the  rails,  giving  an  area  of  250  sq.  ft.  The 
tunnel  is  lined  throughout.  Tunnel  No.  2,  which  is  being 
left  as  a  heading,  is  6.6  ft.  high  x  10.2  ft.  wide,  and  is  lined 
only  where  necessary.  Cross-headings  every  660  ft.,  mak- 
ing an  angle  of  56°  with  the  axis  of  the  main  tunnel  con- 
nect the  two  tunnels.  The  two  parallel  headings,  each 
59  sq.  ft.  in  area,  are  driven  by  machines,  the  work  being 
carried  on  day  and  night  7  days  in  the  week.  No.  I  is  then 
enlarged  to  full  size  by  hand  drilling  (one  holding  and  one 
striking).  No  timbering  is  required  in  the  north  heading. 
Steel  centers  are  used  for  placing  the  masonary  arches.  On 
the  south  headings  a  softer  rock  is  encountered,  requiring 
timbering.  The  excavated  material  is  hauled,  on  a  track 
having  2.6-ft.  gage  in  2-yd.  cars  drawn  by  a  small  locomo- 
tive designed  with  a  very  large  boiler  to  avoid  firing  in  the 
tunnel — a  feature  worthy  of  note. 

The  drilling  machines  are  of  the  Brandt  rotary  type  that 
cuts  a  core.  A  small  four-wheeled  truck  carries  a  horizontal 
beam,  the  shorter  arm  of  which  supports  the  horizontal  bar 
on  which  the  drills  are  mounted,  the  longer  arm  being  coun- 
terweighted.  The  bar  is  braced  against  the  sides  of  the  tun- 
nel much  as  an  ordinary  column  is  held,  except  that,  instead 
of  screw  jacks,  a  plunger  operated  by  water  pressure  is 
used.  Three  or  four  machines  are  mounted  on  the  bar.  The 
drill  is  rotated  by  water,  acting  under  pressure  in  two  pis- 
tons, from  which  screw  gearing  conveys  the  motion  to  the 
drill  rod.  The  total  loss  of  power  by  friction  is  not  over 
30  per  cent.  The  drill  makes  only  5  to  10  revolutions  per 
min.,  according  to  the  nature  of  the  rock.  The  water  for 
running  each  drill  is  240  gals,  per  min.  delivered  under  the 
enormous  pressure  of  1,470  Ibs.  per  sq.  in.  The  water  en- 
ters the  tunnel  in  wrought  iron  pipes,  3^  ins.  inside  diam. 


334        ROCK  EXCAVATION— METHODS  AND  COST. 

and  3/i6  m-  thick,  made  in  lengths  of  26  ft.  In  3,750  ft.  of 
tunnel  the  loss  of  pressure  due  to  friction  in  the  pipes  is  147 
Ibs.  per  sq.  in.  The  drill  itself  is  a  hollow  pipe  of  tough 
steel,  21/4.  ins.  outside  diam.,  provided  with  3  or  4  sharp 
teeth,  and  it  virtually  chips  or  saws  its  way  into  the  rock 
without  pulverizing  it  as  does  a  diamond  drill.  The  ma- 
chine has  a  feed  of  2  ft.  2  ins.,  and  when  the  drill  reaches 
the  end  of  the  feed,  it  is  pulled  out,  unscrewed  and  an  ex- 
tension tube  is  screwed  on,  the  whole  operation  taking 
only  15  to  25  sees.  (Note:  This  is  a  remarkably  short  time 
compared  with  the  ordinary  percussion  drill.)  The  water 
after  passing  through  the  motors  passes  down  through  the 
drill  tube  and  serves  to  wash  out  the  chips  and  keep  the  bit 
cool.  A  hydraulic  piston  advances  the  machine  and  gives  a 
pressure  of  10  tons  on  the  bit.  The  holes  drilled  are  com- 
paratively shallow,  4  ft.  7  ins.  and  2^  ins.  diam.  Three 
machine  drills  put  down  10  to  12  of  these  holes  in  gneiss  in 
2J/2  hrs.,  or  at  the  rate  of  15  to  18  ft.  per  hour  per  drill; 
thus  enabling  an  advance  of  18  to  19^  ft.  to  be  made  in 
heading  (59  sq.  ft.)  every  24  hrs.  The  record  thus  far 
made  for  a  month's  work  is  682  ft.  in  the  north  heading,  for 
December,  1903. 

During  the  last  three  months  of  1899  the  work  done  was 
as  follows :  In  the  north  headings  there  were  three  ma- 
chines in  tunnel  No.  I  and  two  in  the  parallel  heading  of 
No.  2.  The  total  distance  driven  in  these  two  headings  was 
2,985  ft.  in  89  days  (24-hr.),  or  an  average  of  16.8  ft.  per 
heading  per  day.  The  average  cross-section  of  each  head- 
ing was  57  sq.  ft.,  so  that  a  total  of  6,409  cu.  yds.  was  ex- 
cavated. This  required  507  attacks  and  3,066  holes  having 
a  total  depth  of  26,600  ft.,  14,700  re-sharpenings  of  the  bits 
and  44,000  Ibs.  of  dynamite.  This  is  equivalent  to  4.16  ft. 
of  hole  and  nearly  7  Ibs.  of  dynamite  per  cu.  yd.  The  aver- 
age period  of  a  drilling  attack  was  2  hrs.  45  mins.,  while 
charging,  firing  and  mucking  took  6  hrs.  35  mins.  There 
were  648  men  and  29  horses  on  inside  work,  and  541  men 
on  outside  work. 


COST  OF  RAILWAY  TUNNELS.  335 

On  the  south  headings,  where  the  rock  is  much  harder, 
there  were  three  machines  in  each  of  the  two  parallel  head- 
ings. The  total  length  excavated,  with  a  cross-section  of  62 
sq.  ft.,  was  2,880  ft.,  or  6,700  cu.  yds.  in  91  days,  or  15.8  ft. 
advance  in  each  heading  every  24  hrs.  This  required  758 
attacks,  7,940  holes  with  a  total  depth  of  33,000  ft.  and  56,000 
Ibs.  of  dynamite.  Thus  in  hard  gneiss  nearly  5  ft.  of  hole, 
and  8^  Ibs.  of  dynamite,  were  required  per  cu.  yd.,  and 
each  bit  drilled  6l/2  ins.  before  re-sharpening.  There  were 
496  men  and  16  horses  working  in  8-hr,  shifts  on  the  inside 
work,  and  346  men  on  outside  work. 

The  organization  of  the  work  is  as  follows:  Two  men 
operate  each  drill,  one  feeding  the  bit  forward,  the  other 
changing  bits.  There  are  three  of  these  drill  gangs  in  a 
heading,  with  one  foreman  and  two  men  in  reserve.  Three 
or  four  holes  are  drilled  in  the  center  to  a  depth  of  3^4  ft-» 
and  7  or  8  holes  are  drilled  around  the  outside  of  the  face  to 
a  depth  of  4.6  ft.  The  fuses  of  the  center  holes  are  brought 
together  and  cut  off  shorter  than  the  others.  The  drill 
carriage  is  run  back;  a  steel  flooring  is  laid  for  a  distance 
of  30  ft.  back  of  the  face  and  covered  with  debris  to  prevent 
damage  to  it  by  flying  rocks.  The  blast  is  fired,  and  imme- 
diately afterward  a  valve  is  opened  letting  five  jets  of  water 
play  upon  the  rock  to  lay  the  dust.  A  truck  is  brought  up, 
and  four  men  clear  a  passage  in  front,  two  using  picks  and 
two  using  shovels,  while  on  each  side  and  behind  are  as 
many  muckers  as  space  will  permit.  The  stone  is  thrown  to 
both  sides  and  into  the  car,  shoveling  being  greatly  facilitated 
by  the  steel  flooring.  The  steel  plates  are  taken  up  when 
cleared,  and  the  car  pushed  forward.  Finally  the  drill  car- 
riage is  run  forward,  as  soon  as  a  way  has  been  cleared,  and 
the  muck  at  the  sides  is  removed  at  leisure  during  the  drill- 
ing. The  time  consumed  in  an  attack  is : 

Bringing  up  and  adjusting  drills  ....  1/3  hr. 

Drilling 1 24  to  2  hrs. 

Charging  and  firing /4  hr. 


336        ROCK  EXCAVATION— METHODS  AND  COST. 
Clearing  away  muck 2  hrs. 


Total 4^  to  $y2  hrs. 

This  attack  usually  results  in  advance  of  3^4  ft.,  or  18  ft. 
in  24  hrs. 

A  mechanical  plow  has  been  tried  for  clearing  away  the 
muck ;  water  jets  have  also  been  tried,  but  thus  far  without 
success. 

Air  is  forced  in  at  the  portal,  which  is  kept  closed  by  doors, 
but  to  carry  away  the  smoke  rapidly  an  8-in.  pipe  (480  ft 
long)  is  lead  up  to  within  45  ft.  of  the  heading  face,  and  air 
is  driven  through  by  a  water  jet.  Each  face  receives  800 
cu.  ft.  of  fresh  air  per  min.  One  jet  of  water  (1/16  in.  diam.) 
from  the  high  pressure  main  supplies  1,000  cu.  ft.  per  min. 
at  the  end  of  480  ft.  of  8-in.  pipe.  See  Engineering  News, 
May  27,  1897,  for  cross-section  and  plan.  See  also  Aug.  13, 
20,  27,  1903,  for  operating  details. 

Tunnel  Near  Peekskill,  N".  Y. — The  following  data  are 
given  in  Engineering  News,  Dec.  17,  1903,  by  Mr.  Geo.  W. 
Lee,  engineer  for  Sundstrom  &  Stratton,  the  contractors 
who  built  the  double-track  tunnel  described.  The  tunnel 
is  only  275  ft.  long,  and  is  on  the  line  of  the  New  York 
Central  R.  R.,  2,y2  miles  north  of  Peekskill.  The  yardage 
as  shown  on  the  plans  was  7,028  cu.  yds.,  but  as  the  rock 
lay  in  strata  dipping  at  an  angle  of  45°,  it  broke  out  on  the 
uphill  side  so  as  to  leave  large  pockets,  in  'consequence  of 
which  the  contractor  took  out  10  per  cent,  more  rock  than 
he  was  paid  for.  Owing  to  the  seamy  condition  of  the  rock, 
and  the  proximity  of  the  tunnel  to  the  main  line  traffic,  very 
light  charges  of  dynamite  were  used,  which  increased  the 
cost  and  delayed  the  progress.  Rand  steam  drills,  3-in.,  were 
used.  A  heading  8  x  10  ft.  was  run  and  the  bench  was  kept 
close  behind.  Rock  from  the  heading  was  removed  in  small 
narrow  gage  cars;  rock  from  the  bench  was  loaded  into 
standard  gage  cars  by  derrick  cars.  The  following  was  the 
cost  of  the  tunnel  excavation  : 


COST  OF  RAILWAY   TUNNELS.  337 

Equipment  (less  present  value),  supplies  and  re- 
pairs   $2,893.52 

Dynamite  and  exploders 1,604.58 

Coal 57o.8o 

Oil,  waste,  etc.  . 92.80 

Lumber  for  houses  and  shops  129.88 

Miscellaneous 92. 10 

Labor   22,212.86 


Total  ................................  $27,596.54 

Average  cost  per  cu.  yd.  paid  for  .............  3.93 

"       "     "      "     taken  out  ............  3.54 

The  tunnel  was  lined  with  1  :2  14  concrete  ;  692  cu.  yds.  in 
the  bench  walls;  932  cu.  yds.  in  the  arch;  the  portal  head 
walls  were  of  1  13  :6  concrete,  324  cu.  yds.    The  cost  of  the 
concrete  was  as  follows  for  the  1,948  cu.  yds.: 
Cement  at  $1.63  per  bbl  .....................  $5.755-5° 

Sand  at  75  cts.  per  cu.  yd  ....................        662.94 

Crushed  stone  at  80  cts.  per  cu.  yd  .............      1,303.20 

Lumber  : 

Mixing  platforms  and  runways   ........  $336.89 

Ribs,  including  hand  sawing  ...........   234.10 

Backing  boards    ......................    134-44 

Lagging  ............................   341.04 

Sheathing   ..........................   268.49 

Plates,  sills,  studs  and  braces   ..........    182.75 


Coal  ......................................  1  18.73 

Oil   ......................................  16.12 

Hardware,  nails,  spikes,  etc  ...................  224.39 

Tools  ................  ......  ...............  181.10 

Freight  on  stone,  cement,  etc  .................  3,089.86 

Labor,  including  supt.,  foreman,  etc  ............  8,036.31 


Total,  $10.72  per  cu.  yd $20,885.86 


338        ROCK  EXCAVATION— METHODS  AND  COST. 

In  the  approaches  to  the  tunnel  and  in  widening  cuts 
south  of  the  tunnel  45,698  cu.  yds.  of  rock  were  removed. 
On  account  of  proximity  to  traffic,  blasting  could  be  done 
only  at  limited  periods,  which  made  the  cost  of  excavation 
high.  Rock  was  loaded  on  flat  cars  with  stiff  leg  derricks 
provided  with  bull  wheels.  The  cost  was  as  follows: 

Equipment  (less  present  value),  supplies  and  re- 
pairs   $11,673.60 

Dynamite  and  exploders  6,588.82 

Coal 2,490.13 

Oil,  waste,  etc 37°-59 

Lumber  for  buildings 634.22 

Miscellaneous 373. 19 

Labor 69,550.66 


Total $91,681.21 

Average  cost  per  cu.  yd.  paid  for 2.24 

"       "     "      "     taken  out 2.01 

Cost  of  Lining  Tunnels. —  (The  data  on  the  tunnel  near 
Peekskill,  just  described,  should  be  consulted  for  data  on 
concrete  lining.)  Drinker  gives  the  following  data  on  the 
lining  of  Carr's  Tunnel  (825  ft.)  on  the  Pennsylvania  R.  R. 
in  1868-1869.  Brickwoik:  609,000  brick  in  the  arch  (5  per 
cent,  broken  and  lost)  ;  10.44  bushels  of  neat  cement  (no 
sand  used  in  the  mortar)  laid  1,000  bricks,  the  mortar  form- 
ing 30  per  cent,  of  the  brick  masonry  ;  the  arch  was  25  ins. 
thick,  245/2-ft.  span  and  9- ft.  rise  : 

Cost  per  M. 

Bricks  f.  o.  b $8.80 

Loss  in  handling 51 

Unloading  and  delivering   1.92 

Laying 5.84 

Cement 5.10 

$22.17 


COST  OF  RAILWAY   TUNNELS.  339 

Bricklayers  received  40  cts.  per  hr. ;  helpers,  17^  cts.  per 
hr. ;  carpenters,  27^  cts.  per  hr. ;  laborers,  17  cts.  per  hr. 

Stonework:  1,730  perches  (25  cu.  ft.)  of  rough  masonry 
for  side  walls,  presumably  sandstone;  187  perches  of  ring 
stone ;  25  perches  wasted  in  dressing.  The  bench  walls  were 
4  ft.  wide  at  the  bottom,  3  ft.  at  the  top  and  13  ft.  high : 

Cost  per  perch. 

Quarrying  (1,730  perches)    $4.80 

Cutting  (1,730  perches)   4.36 

Hauling  (1,942  perches) 1.06 

Handling  and  laying  (1,917  perches)    2.80 

Cement,   1.65  bu.  per  perch   (8  1/6  per  cent,  of  the 
masonry 81 


Total   $13.83 

Stone  cutters  and  masons  received  35  cts.  per  hr. ;  quarry- 
men,  17^  cts.;  laborers,  17  cts.  The  stone  side  walls  were 
laid  in  8  courses  averaging  2  ft.  thick  each;  hence  there 
were  52,800  sq.  ft.  of  beds  cut;  and  estimating  each  stone 
3  ft.  long  and  dressed  for  1^/2  ft.  back  of  the  face  on  joints, 
there  were  14,300  sq.  ft.  of  joints;  making  a  total  of  67,100 
sq.  ft.  of  cutting  which  cost  11.2  cts.  per  sq.  ft.  This  is 
said  to  have  been  too  high  a  cost,  if  the  measurements  were 
correct. 

Arch  centering  cost  $1,400,  to  which  was  added  $600  for 
moving  the  centering  forward  from  time  to  time;  making 
$2.40  per  lin.  ft.  of  tunnel,  to  which  must  be  added  $0.70  per 
ft.  for  scaffolding. 

In  Engineering  News,  Oct.  25,  1894,  is  given  an  abstract 
of  a  paper  read  before  the  Montana  Society  of  C.  E.'s,  by 
Mr.  H.  C.  Relf,  on  the  lining-  of  the  Mullan  Tunnel  on  the 
Northern  Pacific  Ry.  with  masonry  to  replace  timber.  The 
tunnel  is  3,850  ft.  long,  20  miles  west  of  Helena.  Falls  of 
rock  and  fires  in  the  tunnel  had  caused  numerous  delays. 
The  original  timbering  consisted  of  sets  4  ft.  c.  to  c.  of  12  x 


340        ROCK  EXCAVATION— METHODS  AND  COST. 

12-in.  timbers,  with  4-in.  lagging.    The  size  was  16  x  20  ft. 
in  the  clear. 

Concrete  side  walls  (3<>in.)  and  four-ring  brick  arch 
were  built  in  place  of  the  old  timbering.  A  7- ft.  section 
was  first  prepared  by  removing  one  post  and  supporting  the 
arch  by  struts.  Two  temporary  posts  were  set  up  and 
fastened  by  hook  bolts;  and  a  lagging  was  placed  back  of 
them  to  make  forms  to  hold  the  concrete.  Several  of  these 
7~ft.  sections  were  prepared  at  a  time,  each  two  being  sepa- 
rated by  a  5-ft.  section  of  the  old  timbering.  The  mortar 
car  delivered  Portland  cement  mortar  (i  to  3)  through  a 
chute,  making  an  8-in.  layer  of  mortar  into  which  broken 
stone  was  shoveled  until  all  the  mortar  was  taken  up  by  the 
stone  voids.  In  10  to  14  days  the  walls  were  hard  enough 
to  support  the  arches  which  were  then  allowed  to  rest  on 
the  walls,  and  the  posts  of  the  remaining  5-ft.  sections  were 
removed,  and  concrete  placed  as  before.  About  4  parts  of 
mortar  were  used  to  5  parts  of  broken  stone,  which  is  a  very 
rich  concrete.  The  average  progress  per  working  day  was 
30  ft.  of  side  wall,  or  45  cu.  yds. ;  and  the  average  cost,  in- 
cluding removal  of  old  timber,  train  service,  engineering, 
superintendence  and  interest  on  plant,  was  $8  per  cu.  yd.  of 
concrete  wall.  From  3  to  9  ft.  of  brick  arch  were  put  in  at 
a  time,  depending  upon  the  nature  of  the  ground.  To  re- 
move the  old  timber  arch,  one  of  the  segments  was  partly 
sawed  through,  and  a  small  charge  of  dynamite  exploded  in 
it;  the  debris  being  caught  on  a  platform  car,  from  which 
it  was  removed  to  another  car  and  conveyed  away.  The 
center  was  then  placed,  and  the  cement  car  used  to  mix  mor- 
tar on.  Brick  were  2.y2  x  2^  x  9  ins.,  four  ringings,  mak- 
ing a  2O-in.  arch  and  giving  1.62  cu.  yds.  per  lin.  ft.  of 
tunnel.  The  bricks  were  laid  in  rowlock  bond.  Two  gangs 
of  3  bricklayers  and  6  helpers  each,  laid  12  lin.  ft.,  or  19.4 
cu.  yds.,  of  brick  arch  per  day.  The  brick  work  cost  $17 
per  cu.  yd.,  making  the  total  cost  of  tunnel  lining  $50  per  lin. 
ft.  The  work  was  still  in  progress  at  the  time  of  writing. 


CHAPTER  XVII. 
COST  OF  DRIFTING,  SHAFT  SINKING  AND  STOP1NG. 

Definitions : 

Adit,  a  small  tunnel  driven  from  the  surface  into  a  hill. 

Breast,  the  face  or  working  end  of  an  adit,  drift  or  stope. 

Cross-cut,  a  small,  underground,  horizontal  opening  driv- 
en across  the  trend  of  the  vein  or  formation. 

Development,  or  Dead  Work,  the  shafts,  drifts,  cross-cuts 
and  other  openings  made  preparatory  to  stoping  the  ore. 

Drift,  a  small,  underground  opening  that  follows  the  di- 
rection of  the  vein  or  lode. 

Incline,  a  shaft-like  opening  extending  downward  from 
the  surface  at  an  angle  of  less  than  90°. 

Level,  a  horizontal  opening  in  a  mine  connecting  with  a 
shaft  or  incline.  Levels  are  usually  100  ft.  apart,  occasion- 
ally 150  ft. 

Raise,  or  Upraise,  an  opening  driven  up  from  one  level 
to  another. 

Shaft,  a  vertical  opening  extending  from  the  surface,  and 
used  as  an  entrance  and  exit. 

Stoping,  mining  the  mass  of  ore  between  levels. 

Winze,  a  small  opening  connecting  one  level  with  another, 
as  for  ventilation. 

General  Considerations. — The  reader  is  supposed  to  be 
tolerably  familiar  with  one  or  more  -  books  on  mining, 
such  as  Ihlseng's,  or  Foster's,  but  a  few  remarks  may  help 
to  a  clearer  understanding  of  the  reasons  why  underground 
work  is  so  much  more  expensive  than  open-cut  work.  As 
we  have  seen  in  the  last  chapter,  wherever  a  narrow  face  in 
a  tunnel  is  exposed  to  attack  by  blasting,  the  explosive  has 
a  great  deal  of  work  to  do  per  unit  of  excavation,  because 
of  the  great  area  per  unit  that  must  be  sheared  off.  To  place 
the  larger  amount  of  explosive  required  means  either  the 


342        ROCK  EXCAVATION— METHODS  AND  COST. 

drilling  of  drill  holes  having  a  large  diameter,  or  the  drilling 
of  holes  close  together.  Miners  in  the  days  of  hand  drilling 
were  obviously  compelled  to  choose  the  latter  method ;  and, 
even  since  the  introduction  of  dynamite  and  power  drills, 
the  practice  has  continued  to  be  close  spacing.  I  am  not 
at  all  sure,  however,  that  this  is  the  best  practice ;  and  I  look 
to  see  more  powerful  drills  used  in  the  future  for  drilling 
holes  of  greater  diameter,  spacing  the  holes  farther  apart. 
The  advantage  of  this  method  has  been  proved  in  subaque- 
ous excavation,  and  there  is  every  reason  for  believing  that 
larger  holes  will  prove  more  economic  in  underground  work. 

In  underground  work,  since  derricks  cannot  be  used,  it 
is  necessary  to  break  up  the  rock  to  sizes  that  will  require 
little  or  no  sledging,  mudcapping  or  blockholing,  before 
loading  by  hand  into  cars.  This  means  likewise  either  close 
spacing  of  drill  holes,  or  drill  holes  of  large  diameter.  We 
see,  therefore,  that  in  any  case  more  work  in  drilling  and 
more  explosives  are  required  to  break  rock  underground 
than  in  open  cuts.  In  addition  to  these  greater  costs  are 
the  costs  of  timbering,  or  filling,  of  pumoinp".  of  lighting,  of 
hoisting,  of  greater  delays  after  blasting,  of  ventilation,  etc. 
Finally,  the  miners'  unions  have  gradually  raised  rates  of 
wages  to  a  point  that  makes  comparison  of  open-cut  work 
with  underground  work  impossible,  if  the  dollar  is  the  unit 
of  comparison. 

Shaft  sinking  is  well  known  to  be  more  expensive  than 
tunneling,  ton  for  ton,  or  yard  for  yard ;  and  it  is  impossible 
to  sink  a  shaft  with  anything  like  as  great  rapidity  as  a  tun- 
nel of  equal  size  can  be  driven.  The  chief  reason  for  the 
slowness  of  shaft  sinking  lies  in  the  fact  that  the  greater 
part  of  the  muck  must  be  removed  after  each  blast  before 
drilling  can  begin ;  whereas  in  a  tunnel  the  drillers  can  be- 
gin while  the  muckers  are  still  at  work.  Timbering  a  shaft 
also  delays  excavation  and  hoisting  to  a  far  greater  degree 
than  tunnel  timbering.  It  is  harder  to  ventilate  a  shaft,  and 
obviously  harder  to  drain  a  shaft  than  a  tunnel.  The  fixed 
expense  of  a  hoisting  plant  and  engineer  is  out  of  all  pro- 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     343 

portion  to  the  small  amount  of  material  hoisted  daily.  All 
these  factors,  and  certain  others  of  less  importance,  make 
shaft  sinking  slower  and  more  expensive  than  tunneling. 
The  number  and  size  of  drill  holes  and  the  amount  of  ex- 
plosives are  practically  the  same  in  shafts  and  tunnels  of 
equal  areas.  As  the  depth  of  the  shaft  increases,  there  comes 
a  time  when  work  is  retarded  by  the  speed  and  capacity  of 
the  hoisting  plant.  The  best  record  of  speed  of  shaft  sink- 
ing for  moderate  depths  is  that  given  by  Mr.  Edward  J. 
Way,  in  the  Trans.  Am.  Inst.  Min.  Eng.,  Feb.,  1904.  A 
shaft,  6  x  21  ft.,  was  sunk  858  ft.  in  five  months;  during 
the  last  month,  May,  1903,  the  record  was  213^  ft.  In  all 
there  were  4,032  holes  drilled  to  an  average  depth  of  7  ft. 
2  ins. ;  418  cases  of  gelatine,  2,475  co^s  °f  ^use»  86  boxes  of 
detonators  and  207  boxes  of  candles  were  used.  This  work 
was  done  in  South  Africa,  and  the  costs  are  given,  but  un- 
fortunately Mr.  May  does  not  give  the  organization  of  the 
force  nor  the  rates  of  wages. 

The  following  examples  of  cost  will  give  a  fair  idea  of 
the  range ;  but  I  trust  that  some  of  my  readers  will  be  kind 
enough  to  send  me  other  detailed  examples,  stating  condi- 
tions, so  that  future  editions  of  this  work  may  be  of  greater 
value  both  to  the  experienced  as  well  as  the  inexperienced 
mining  man. 

Cost  of  Tunneling  Melones  Mine. — In  Trans.  Am.  Inst. 
Min.  Eng.,  1898,  Mr.  W.  C.  Ralston  gives  data  of  cost  of 
driving  an  adit  at  the  Melones  Mine,  Calveras  Co.,  Cal.,  in 
1898.  The  work  consisted  in  extending  a  tunnel  that  was 
already  1,080  ft.  long.  The  tunnel  was  7  x  8  ft.  in  the  clear; 
grade,  l/4  per  cent.;  12-lb.  rails;  22-in.  gage;  ties,  4x6 
ins.,  3  ft.  c.  to  c. ;  walking  plank,  2  x  20  ins.  An  Ingersoll- 
Sergeant  compressor,  class  "B,"  driven  by  a  5-ft.  Pelton 
water  wheel,  delivered  air  to  an  8-in.  pipe  at  a  pressure  of 
200  Ibs.  When  water  was  scarce  a  Nagle  engine,  12  x  16, 
was  used.  A  No.  4^  Baker  blower,  run  as  an  exhaust, 
sucked  air  through  a  n-in.  pipe. 

In  255  days  only  2  were  lost.    The  average  progress  was 


344        ROCK  EXCAVATION— METHODS  AND  COST. 

10.22  ft.  per  day,  or  306.9  ft.  per  month,  working  from  one 
face.  The  best  run  for  two  consecutive  weeks  was  184  ft., 
or  92  ft.  per  week.  The  rock  was  firm  greenstone  (diabase) , 
brown  slate  and  talc  schists  filled  with  quartz  stringers. 
Only  nine  sets  of  timbers  were  used.  The  work  was  rushed, 
and  no  especial  effort  was  made  to  economize.  Three  8-hr, 
shifts  of  7  men  each  (4  drillers  and  3  muckers)  were 
worked.  Two  12-hr,  shifts  were  worked,  each  with  a  team 
and  driver  and  an  engineman.  One  lo-hr.  shift  was  worked 
with  a  blacksmith  and  helper,  a  mechanic  and  an  outside- 
man.  Total,  29  men.  Two  Ingersoll  drills,  3^-in.,  were 
used,  and  the  repairs  on  them  were  only  $91  for  over  2,600 

ft.  of  tunnel. 

MELONES  MINE  (1898). 

Actual  cost  (exclusive  of  management)  of  2,608.5  ft.  of  tunnel. 

Cost  per 
Lin.  Ft. 

Labor    (29   men) $19,501.46      $7.47 

Powder,  2,000  Ibs.  No.  i  Hercules  @  16.6  cts...  j 

Powder,  25,500  Ibs.    No.   2   Hercules    (40%)    ©[3,405.65        1.30 

11.9  cts ' 

Fuse,  74,000  ft.  @  51.7  cts.  per  100 


Caps,  200  boxes  @  60  cts.  per  100 C 

Wood,  333^  cords  @  $5 1,667.50  .63 

Water,  15  cts.  per  inch 828.50  .32 

Coal,  11,591  Ibs.  Cumberland  @  $15 179-43  -06 

Foot  plank,  ties,  and  9  sets  of  timbers,  8,466  ft. 

B.  M.  @  $20  per  M 169.32  .06 

Candles,  3,040  Ibs.  @  7l/2  cts 262.04  .10 

Steel  rails,  21,555  Ibs.',  ilA  and  2^/4  cts 567.62  .22 

Air  pipe,  n-in.,  18  cts.  and  30  cts \ 

Air  pipe,  3-in.,  22  cts |  1,042.45  .45 

Water  pipe,  2-in.,   ii*4  cts ) 

Horse  feed :  hay,  il/2  cts. ;  barley,  .019  ct 267.16  .10 

Steel,  drill  parts,  oil  and  tools,  etc ' 316.92  .12 


Total $28,708.25    $11.02 

N.  B. — The  air  and  water  pipes  used  in  running  different  cross 
cuts  were  not  left  in  place,  but  were  moved  as  needed.  Of  the  21 
miners,  six  received  $3  a  day,  the  rest  $2.50  a  day,  and  carmen  $2 
a  day.  Powder  was  used  liberally  to  pulverize  the  ore. 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     345 

Cost  of  Tunneling,  Hogsback  Mine. — At  the  Hogsback 
Mine,  Placer  Co.,  Cal.,  the  force  was  21  men  divided  into  3 
8-hr,  shifts  of  5  men  each;  two  12-hr,  shifts  of  an  en- 
gineer, driver  and  horse  on  each  shift ;  and  two  ic-hr.  shifts 
of  blacksmith.  The  average  hardness  was  the  same  as  at 
the  Melones  Mine,  but  the  blocky  nature  of  the  ground  per- 
mitted more  effective  blasting,  and  only  half  as  many  holes 
were  drilled. 

HOGSBACK  MINE  (1888). 

Actual  cost  (exclusive  of  management)   of  1,559.6  ft.  of  tunnel. 
7  X  8  ft. 

Cost 
per  Ft. 

Labor    $12,131.49  $7.77 

Powder,   10,021  Ibs.  No.  2  @  14)^  cts 1,478.10  .90 

Fuse,  23,045  ft.  @  54^  cts.,  caps  @  80  cts 165.59  .10 

Wood,  522  cords  @  $2.75 1,435-5^  -92 

Charcoal,  1,580  bu.  @  20  cts 316.00  .20 

Candles,  1,755  Ibs.  @  13*4  cts 23253  .14 

Gang  plank  and  ties,  7,624  ft.  B.  M.  @  $22.50. .  171.54  .10 

Timbers,  21   sets  @  $1.80 37-8o  .02 

Steel  rails,  etc.    (i6-lb.),  20,048  Ibs.  @  4  cts..          801.92  .51 

Air  and   water  pipes,  3-in.   @  29^/2   cts. ;    i-in. 

@   &/4    cts 761.43  .48 

Horse  feed:  hay,  3  cts.;  barley,  3  cts.  per  Ib.  .          349-6o  .22 

Steel,   drill   parts,   oil,   tools,   etc 916.33  .58 


Total    $18,797.83          $11.94 

N.  B. — Each  man  received  $3  a  day. 

COMPARISON  OF  BEST  WEEK'S  RECORD  IN  EACH  MINE. 

Melones.       Hogsback. 

No.  of  men 31  20 

No.  of  holes  drilled,  5  ft.  each 291*  150! 

Holes  reblasted   6  n 

Time  used  in  drilling 45      hrs.*      26     hrs.f 

Average  time  drilling  per  shift 2^  hrs.  ij4  hrs. 

Powder,    Ibs 925  344 

Candles,   Ibs 77  72 

Wood  consumed,  cords   None.  21 

*  6.47   ft.    of  hole    per   hr.   of   actual    drilling. 
t  5.77    ft.    of    hole    per   lir.   of   actual    drilling. 


346        ROCK  EXCAVATION— METHODS  AND  COST. 

Rock  extracted  per  shift,  cars 23.19  21.8 

Rock  extracted  for  week,  3  shifts,  7  days.        487  cars.         458 

Progress  for  week,  ft 92  73.6 

Cu.  yds.  solid  rock  (7X8) 191  149 

Previously  reported   2,310  404 

Labor  expenses  for  week $55175  $43575 

Observe  that  a  7  x  8-ft.  tunnel  has  2.08  cu.  yds.  solid  rock 
per  running  ft.,  and  taking  the  average  runs  at  the  two  mines 
we  have: 

Per  Cu.  Yd.  Rock  in  Place. 
Melones.  Hogsback. 

Powder,   No.   2,  40%    Hercules 5^  Ibs.  3%  Ibs. 

ruse    i3l/2  ft.  7     ft. 

Labor  (exclusive  of  management)  ....  $3.60  $37° 

Ft.  of  hole 7-6  5 

Observe  that  each  car  held  about  4/10  cu.  yd.  solid  rock  at 
Melones  and  1/3  cu.  yd.  at  Hogsback. 

Cost  of  Sinking  and  Sloping  at  the  Utica  Angels. — In 
Trans.  California  Miners'  Assoc.,  1899,  Mr.  J.  H.  Collier, 
Jr.,  gives  the  following  data  on  mining  at  the  Utica  Angels, 
Calaveras  county,  Cal. :  The  mine  is  in  a  mineralized  zone 
of  crushed  diabase  more  or  less  altered  to  schist,  being  in  the 
celebrated  "Mother  Lode."  The  ore  is  a  nearly  vertical 
quartz  vein  carrying  free  gold  and  pyrites.  The  method  of 
timbering  and  stowing  or  filling  is  used,  no  opening  over  16 
ft.  high  being  left.  Waste  from  prospect  cross-cuts  is  used 
for  stowing. 

In  stoping  two  lo-hr.  shifts  of  50  men  per  shift,  supply  a 
6o-stamp  mill  with  300  tons  of  ore  per  day.  The  cost  of 
labor  in  stoping  is  as  follows  per  shift : 

12  miners,  at  $3 $36.00 

12  helpers,  at  $2.50   30.00 

15  shovelers,  at  $2.50 37-5° 

6  men  tramming,  at  $2.50 JS-00 

5  timbermen,  at  $3   I5-OO 


Total  labor  stoping  150  tons $133.50 

The  ore  is  loaded  for  hoisting  into  skips  from  chutes. 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     347 

In  shaft  sinking,  after  removing  the  surface  soil,  men 
begin  with  churn  drills,  having  a  2-in.  bit  to  start  with,  and 
tapering  to  i%  ins.  at  a  depth  of  6  or  7  ft.  After  reaching 
solid  rock  four  air  drills  are  used,  two  at  each  end  of  the 
shaft  on  bars  about  3  ft.  above  the  bottom.  Eight  rows  of 
holes  are  drilled  across  the  short  way  of  the  shaft,  three 
holes  to  a  row,  6  to  7  ft.  deep ;  six  holes  making  the  V-cut. 
Each  hole  is  charged  with  6  to  9  sticks  (i^g  x  8  ins.)  of  40 
per  cent,  dynamite,  and  the  firing  is  done  with  a  battery. 
The  force  consists  of  6  machine  men  and  6  helpers,  divided 
in  three  8-hr,  shifts;  2  enginemen  on  12-hr,  shifts;  2  ma- 
chine men  with  2  helpers  and  3  timber  men,  who  work  only 
when  machines  run.  Each  man  receives  $3  per  shift.  A 
three-compartment  shaft  (7  x  16  ft.  outside  of  timbers), 
compartments  4  1/3  x  5  ft.  each,  was  sunk  825  ft.  in  7  months. 
The  timber  sets  are  5  ft.  apart  and  2-in.  lining  is  used.  The 
author  gives  a  good  description  of  framing  and  placing  the 
timbers. 

Drifts  are  timbered  with  two  7-ft.  legs  set  6  ft.  apart  at 
the  bottom  and  a  5-ft.  cap  on  the  top.  Machine  drills  put 
in  three  horizontal  rows  of  holes,  four  holes  in  a  row,  the 
center  holes  forming  a  vertical  V-cut.  In  talc  and  mica- 
schist  the  drill  clogs  badly  on  down  holes.  In  one  case  a 
7-ft.  dry  (up)  hole  was  drilled  in  y2  hr.,  whereas  it  took  2 
hrs.  to  drill  a  7  ft.  down  (wet)  hole.  A  jet  of  water  under 
pressure  enables  the  drills  to  cut  much  faster  on  down  holes. 

Cost  of  Sinking  and  Drifting  at  the  Lincoln  Gold  Mine.— 

The  cost  of  sinking  the  Lincoln  shaft  at  Sutter  Creek, 
Amador  county,  Cal.,  is  given  in  detail  in  the  fifth  annual 
report  of  Mr.  E.  C.  Voorheis,  Superintendent  of  the  Lincoln 
Gold  Mine  Development  Co.  Mr.  Voorheis  has  given  me 
certain  additional  data  not  contained  in  the  regular  report, 
as  follows : 

In  shaft  sinking  the  men  work  8-hr,  shifts,  but  in  drifting 
10-hr,  shifts.  The  average  depth  of  each  drill  hole  in  shaft 
sinking  is  about  6  ft.,  but  in  drifting  5  ft.  The  drilling  was 
done  by  power,  using  the  "Baby"  giant  drill  manufactured 


348        ROCK  EXCAVATION— METHODS  AND  COST. 

by  the  Compressed  Air  Machinery  Co.,  of  San  Francisco. 
The  powder  used  was  Herclues,  40  per  cent,  nitroglycerin, 
and  the  fuel  for  steaming  was  crude  oil  delivered  at  the 
mine  at  $1.50  per  bbl.,  of  42  gallons. 

The  work  of  sinking  the  Lincoln  shaft  was  completed 
May  24,  1902,  sinking  from  a  level  of  1,260  down  to  the 
2,ooo-ft.  level,  a  distance  of  740  ft. 

The  size  of  the  excavation  is  8  x  17  ft.  Material  en- 
countered in  sinking,  greenstone  and  hard  black  slate. 

The  labor  cost  of  sinking  and  putting  in  timbers  was  as 
follows :  It  required  3,864  blasting  holes  drilled  in  the  bot- 
tom of  the  shaft,  or  5.2  per  foot  of  shaft,  which  took : 

2,956  days'  labor  at  $2.75  per  8-hr,  day $7,129.00 

i  day  foreman,  350  days,  at  $4 1,400.00 

i  night  foreman,  282  days,  at  $3.25  916.50 


Total  labor  cost  of  sinking  740  ft.  and  putting 

in   fimbers    $9,445.50 

Labor  cost  per  ft.  of  sinking  740- ft.  shaft.  .$12.76 

12,450  Ibs.  Hercules  powder  used,  costing  1,307.25 

Cost  of  powder  per  ft.  of  shaft 1.77 

Amt.  of  powder  per  ft.  of  shaft,  16.8  Ibs. — 

35,800  ft.  of  fuse  used,  costing 125.30 

Cost  of  fuse  per  foot  of  shaft 17 

Amt.  fuse  per  ft.  of  shaft,  48.4  ft. — 
46  boxes  of  Lion  caps  were  used,  costing.  .  46.00 

Cost  of  caps  per  ft.  of  shaft 06 

2,400  Ibs.  of  candles  used,  costing 288.00 

Cost  of  candles  per  ft.  of  shaft 39 

Amt.  candles  used  per  ft.  of  shaft,  3.2  Ibs. — 
148  sets  of  timbers,  requiring  207,200  ft.  of 

lumber;  average  cost,  $18  per  M 3,729.60 

Cost  of  lumber  per  ft.  of  shaft 5.04 

Amt.  lumber  per  ft.  of  shaft,  280  ft. — 

Total  cost,  labor,  lumber,  light,  etc.  .  .  $14,941.65 


Cost  per  ft.  for  labor,  lumber,  light,  etc.$2O.i9 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     349 

Total    cost,    labor     for    engineers,   black- 
smiths, framing  timbers,  skip  tenders .  .  $6,224.00 

Cost  of  top  expense  per  ft.  of  shaft $8.41 

Total  cost  for  fuel  for  sinking  740  ft 5*893.50 

Cost  of  fuel  per  ft.  in  sinking  740  ft 7.96 

Total  cost  of  sinking  shaft,  including 

all  expenses  except  office  expense..  $27,059.15 


Total  cost  per  ft.  of  shaft $36.56 

During  the  time  the  shaft  was  being  sunk  60,025  tons  of 
water  were  hoisted,  or  14,406,200  gallons.  9,456  tons  of 
waste  were  hoisted  from  the  bottom  of  the  shaft  to  the  sur- 
face, which  added  to  the  water  would  make  a  total  of  69,481 
tons  hoisted  to  the  surface  during  the  time  the  shaft  was 
being  sunk. 

On  July  i  cross-cutting  for  the  vein  channel  was  begun, 
starting  from  the  north  side  of  the  shaft  and  gradually 
turning  to  the  west,  until  a  point  at  right  angles  to  the  foot 
wall  of  the  shaft,  which  is  at  right  angles  to  the  formation 
of  the  ground,  was  reached.  This  cross-cut  has  been  ex- 
tended in  a  westerly  direction  642  ft.  At  a  point  187  ft. 
west  of  the  foot  wall  of  the  shaft  the  cross-cut  passed 
through  a  fissure  of  soft  black  slate,  40  to  60  ft.  wide,  car- 
rying a  good  deal  of  water  on  the  hanging  wall  side  and 
some  stringers  of  quartz,  which  was  supposed  to  be  the 
channel  that  carried  the  ore  bodies  on  the  upper  levels.  We 
drove  north  on  the  foot-wall  side  of  this  fissure  233  ft.  and 
south  250  ft.,  making  in  all  483  ft.  driven  on  the  channel. 
At  the  end  of  each  drift  we  cross-cut  both  east  and  west 
12%  ft.  each  way,  which  is  room  enough  to  run  cross-cuts 
with  the  diamond  drill. 

The  following  is  a  detailed  statement  of  the  cost  of  run- 
ning 1,175  ft-  of  drifts  and  cross-cuts  on  the  1,950- ft.  level. 
Most  of  the  rock  was  hard  greenstone ;  average  size  of  tun- 
nel, 5  x  8  ft. : 


350        ROCK  EXCAVATION— METHODS  AND  COST. 

1,428    days'    labor,    * $3,772.50 

1 68  days  for  day  foreman  at  $4 672.00 

134  days  for  night  foreman  at  $3.25 435-5° 

Total  labor  cost  for  drifting  and  cross- 
cutting  1,175  ft $4,880.00 

Average  labor  cost  per  ft $4-153 

11,150  Ibs.  of  powder  used,  costing   1,226.50 

Average  cost  of  powder  per  ft '1-043 

26,500  ft.  of  fuse  used,  costing   79-5° 

Average  cost  of  fuse  per  ft 068 

35  boxes  of  Lion  caps  used,  costing 35-°° 

Average  cost  of  caps  per  ft 03 

800  Ibs.  of  candles  used,  costing 96.00 

Average  cost  per  ft.  for  candles 082 


Total  cost  per  ft $5-376" 

Total  cost  $6,317.00 

3,258  blasting  holes  were  drilled.  Average  number  of 
holes  drilled  per  ft.,  2.77. 

The  average  amount  of  powder  used  for  each  blasting 
hole  was  3.42  Ibs.  of  40  per  cent.  Hercules. 

Average  amount  of  fuse  per  ft.,  22  ft. ;  average  number 
of  caps  per  ft.,  3;  average  amount  of  candles  per  ft.,  0.68  Ib. 

Cost  of  the  Newhouse  Tunnel. — In  the  Engineering  and 
Mining  Journal,  April  19,  1902,  Mr.  H.  Foster  Bain  gives 
the  following:  The  Newhouse  tunnel  starts  at  Idaho 
Springs,  Col.,  at  an  altitude  of  7,543  ft.  It  is  a  12  x  12-ft. 
excavation  now  12,861  ft.  long,  and  eventally  will  be  5 
miles  long.  In  Feb.,  1902,  the  average  progress  was  9.2  ft. 
per  day  from  one  face,  or  267.6  ft.  for  the  month.  The 
rock  never  breaks  beyond  the  holes ;  it  is  a  granite-gneiss 
and  schist  dipping  away  from  the  face.  Twenty  holes,  10  ft. 
deep,  are  drilled,  8  cut  holes,  I  plunger  hole  at  the  upper 
center  of  the  cut,  3  back  holes  along  the  roof,  looking  up. 
and  4  side  holes  on  each  side  looking  a  little  out  and  up. 


Miners  at  $2.75  per   lo-hr.   day  and  car-men  at  $2.50. 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     351 

Three  Leyner- Water  drills  are  used;  two  3-in.  sluggers  on 
two  columns  drilling  the  side  and  cut  holes,  and  one  Model 
5  drill  mounted  on  a  bar  drilling  the  plunger  hole  and  the 
back  holes.  The  drill  crew  consists  of  5  men,  who  work 
from  7  A.  M.  to  about  5  P.  M.  ;  they  do  not  stop  drilling  at 
noon.  At  I  p.  M.  a  powder  gang  of  5  men  comes  on  and 
attends  to  track  laying,  timbering,  putting  in  water  box, 
etc.,  until  the  drilling  is  done.  They  lay  the  permanent 
track,  which  is  kept  250  ft.  from  the  face;  the  temporary 
mucking  track  being  run  up  the  drilling  platform.  The 
tracks  are  i8-in.  gage,  35-lb.  rails,  on  4  x  8-in.  x  8-ft.  ties. 
The  water  box  is  i  x  2  ft.,  made  of  2-in.  stuff  and  is  car- 
ried under  the  track.  The  powder  gang  tears  down  the 
drills,  covers  the  floor  with  ^-in.  steel  plates  in  sections  6  ft. 
square  for  40  ft.  back  of  the  face,  and  then  fires  the  cut 
holes  by  electricity;  this  takes  40  mins.  The  cut  is  fired  2 
to  5  times  with  60  per  cent,  gelatin  powder,  8  to  9  sticks 
being  used  for  the  first  round.  In  all  about  100  Ibs.  are 
used  in  the  cut  holes.  The  side  and  back  holes  are  fired 
with  40  per  cent,  powder,  50  to  70  Ibs.  being  used.  The 
holes  are  not  tamped,  and  the  blasting  takes  2^2  to  3^  hrs. 
During  the  blasting  compressed  air  is  delivered  to  the  face 
through  a  4-in.  pipe,  and  drives  the  smoke  back  to  a  .iQ-in. 
exhaust  pipe  laid  between  the  rails  on  top  of  the  water  box. 
After  blasting,  the  gang  cleans  up  the  track  ready  for  the 
muckers  and  loads  the  first  train  of  cars. 

At  10  P.  M.  a  mucking  gang  of  6  men  goes  on ;  the  boss 
picks  down,  and  three  men  shovel  while  two  rest.  The  cars 
(3  x  3^  x  5  ft.)  hold  35  cu.  ft.,  and  45  to  60  cars  are  filled 
per  night.  Mules  have  been  used  for  tramming,  but  a  16- 
H.  P.  Baldwin-Westinghouse  electric  locomotive  has  juct 
been  installed.  In  all  there  are  32  men  employed  on  com- 
pany work,  including  blacksmiths. 

The  power  plant  includes  three  8o-H.  P.  boilers,  of  which 
two  are  in  use  at  one  time ;  two  16  x  i6-in.  two-stage  Nor- 
walk  compressors ;  one  22  x  24-in.  two-stage  compressor ; 


352        ROCK  EXCAVATION—  METHODS  AND  COST. 

one  No.  7  Root  blower  driven  by  a  5<>H.  P.  Atlas  engine; 

3O-H.  P.  engine  driving  the  2O-kilowatt,  5OO-volt  dynamo. 

For  drilling  the  air  is  used  at   160  Ibs.  pressure,  having 

been  gradually  worked  up  from  no  Ibs. 

Each  of  the  drill  crew  receives  $3  a  day  plus  $i  on  an 

average  for  bonus.    The  total  bonus  is  $6  per  ft.  for  all  over 

1  60  ft.  per  month,  or  about  $500,  and  is  money  well    ex- 

pended, the  men  working  long  hours  and  hard  rather  than 

lose  a  round. 

The  detailed  cost  per  foot  is  shown  by  the  following  ab- 

stract from  the  manager's  report  for  the  year  ending  Aug. 

31,  1900: 
Labor  : 

Drill  crews  and  foremen   .................  $3-Oi 

Trammers,  blasters  and  drivers   ...........   4.34 

Blacksmith  shop  ........................    1.03 

Engineers    .....  ........................    1.15 

Explosives  ..............................   4.55 

Oil  and  waste  .....................  .  .....  12 

Coal   ..................................   3.91 

Mules,  feeding  and  shoeing   ...............  32 

Drill  repairs   .............................  82 

Premiums    .............................    1.87 

Tools   ..................................  33 

Timber    ................................  16 

Track  and  material  ......................    1.84 

Track  —  labor  and  repairs  .................   2.07 

Engineering  and   surveying    ...............  22 

Salaries  and  office  expenses  ..............    1.97 

Miscellaneous  — 

Legal  expense    .....................  $0.07 

Insurance   .........................  1  1 

Taxes    ............................  12 

Minor  items  ........................  73 


$28.74 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.    353 

Total,  $79,478  for  driving  2,959^  feet  or  $28.80  per  foot. 
The  previous  year  this  cost  was  $27.74  and  the  actual  break- 
ing cost  was  $19.68.  The  increase  was  due  to  the  increased 
cost  of  supplies  and  the  greater  expense  of  working  in  a 
larger  tunnel. 

Cost  of  Sinking  and  Drifting  at  the  Homestake  Mine. — In 
Mining  and  Scientific  Press,  Feb.  13  to  Mar.  12,  1904,  Mr. 
Bruce  C.  Yates-  gives  data  on  the  methods  and  costs  of  min- 
ing work  in  the  Homestake  Mine,  Lead,  S.  D. 


§•  54- 


Fig.  54  shows  the  location  of  drill  holes  in  shaft  sinking. 
The  rock  is  a  hard  carbonaceous  slate  dipping  at  an  angle 
of  60°  to  90°  from  the  horizontal,  which  makes  blasting  the 
cut  quite  difficult.  When  sinking  is  resumed  in  any  of  the 
shafts,  a  25-H.  P.  engine,  operated  by  reheated  compressed 
air,  is  installed  on  the  lowest  level.  Miners  in  the  shaft  usu- 
ally work  under  contract.  At  the  Ellison  shaft,  which  has 
three  compartmnts,  two  of  which  are  5  x  10  ft.,  and  the 
third  6  x  10  ft.  in  the  clear,  the  force  employed  on  each 
shift  is:  4  miners  (contractors),  i  engineman,  i  lander,  i 
timberman  and  i  carpenter  working  2^  shifts  framing  one 
set  of  timbers  which  provide  for  6  ft.  of  shaft.  The  actual 


354        ROCK  EXCAVATION— METHODS  AND  COST. 

time  in  placing  one  set  of  timbers  is  8  hrs.,  but  the  timber- 
men  are  kept  busy  one  shift  in  each  24  hrs.  running  timber 
from  the  saw  mill  and  putting  in  extra  bracing.  The  length 
of  a  shift  is  10  hrs.,  but,  as  the  men  are  lowered  twice  each 
shift  on  company  time,  the  actual  working  time  is  about 
9  hrs. 

The  cost  of  labor  in  sinking  i  ft.  is : 

4  miners,          2  shifts,  at  $4 $32.00 

i   timberman,   I       "        "    4 4.00 

i   engineman,  2  '    4 8.00 

i   lander,  2       "        "    3 6.00 

Total  labor  cost  per  ft $50.00 

To  this  must  be  added  the  cost  of  timber  sets  (12  x  12-in. 
timbers),  as  follows: 

Timber  for  i  set,  1,500  ft.  B.  M $26.85 

Framing  i   set   10.00 

4  miners,  one  shift,  $4 16.00 

i  lander  "       3 3.00 

i   timberman  4 4.00 

i   engineman  4 .< 4.00 


Total  cost  per  set   $63.85 

Cost  per  ft.  of  shaft,  $10.64.  The  costs  of  the  lining,  of 
explosives  and  of  power  are  not  included  in  the  foregoing. 

There  are  three  sizes  of  drifts  '.6x7  ft.  for  prospect 
drifts ;  7  x  8  ft.  for  single-track  working  drifts ;  12  x  8  ft. 
for  double-track  working  drifts.  Figs.  55  and  56  show  two 
methods  of  locating  holes  in  single  track  drifts ;  holes  are 
6  ft.  deep,  and  the  advance  is  5  ft.  Two  machines  are  used 
for  drilling,  preferably  mounted  on  a  horizontal  bar.  The 
bar  set  up  is  preferred  to  the  column  set  up,  because  the 
machines  can  be  set  up  immediately  after  blasting,  and  be- 
cause the  sides  of  the  drift  are  carried  along  much  more 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOP  ING.    355 

evenly.    The  following  shows  the  cost  of  driving  5  ft.  of  7 

x  8-ft.  drift : 

i  miner  drilling,       2  shifts,  at  $3.50 $7.00 

i  helper       "  2     "         "     3.00 6.00 

i  miner  blasting,       i     "         "     3.50 3.50 

i  helper  i  3.00 3.00 

i  shoveler 


2  3.00 6.00 

Explosives,  40  p.  c.  dyn.,  cap  and  fuse 10.75 

Blacksmith,  repairs  of  drill  and  mch.  shop.  .  .   4.85 


Total  cost  of  5  ft $41.10 

Cost  per  ft 8.23 

Cost  per  ton 1.47 


l^^m^m^i 


w 
t 


Fig.  55- 


Fig.  56. 


The  above  does  not  include  track  laying  or  putting  in  air 
pipe.  There  is  no  timbering  in  drifts.  Dynamite  costs  about 
12  cts.  per  Ib.  The  drills  used  are  3  or  3^  ins.  When  two 
drills  are  worked,  one  helper  serves  two  drills,  and  the 
progress  is  nearly  doubled.  The  cars  have  a  capacity  of 
20  cu.  ft.  each,  and  hold  10  cu.  ft.  of  solid  rock,  weighing 
i  ton.  Hauling  is  done  with  horses  at  a  cost  of  0.3  ct.  per 
ton  per  1,000  ft. 

The  cost  of  driving  a  double-track  8  x  12  ft.,  drift,  re- 


356        ROCK  EXCAVATION— METHODS  AND  COST. 

quiring  20  holes  6  ft.  deep,  giving  an  advance  of  5  ft.,  is  as 

follows : 

i  miner  drilling,    3  shifts,  at  $3.50 $10.50 

i  helper  3       "        "     3.00 9.00 

i  miner  blasting,  i       "        "     3.50 3.50 

i  helper        "         i       "        "     3.00 3.00 

i  shoveler  3       "        "     3.00 9.00 

Explosives,  caps  and  fuse  16.90 

Blacksmith,  repairs  and  mch.  shop 6.50 


Total  cost  of  driving  5  ft $58.40 

Cost  per  ft 11.68 

Cost  per  ton  1.22 

Cross  cuts  and  drifts  in  ore  are  from  1 8  to  24  ft.  wide  and 
10  to  12  ft.  high. 

In  making  a  "raise,"  6x6  ft.,  one  machine  driller  and 
helper  will  make  100  ft.  of  raise  in  60  shifts,  provided  they 
are  not  required  to  "car"  the  rock;  the  location  of  holes  is 
similar  to  that  in  drifting. 

Cost  of  Drifting  and  Sloping  at  Cripple  Creek. — In  The 
Engineering  and  Mining  Journal,  Nov.  21,  1903,  Mr.  J.  R. 
Finlay  gives  the  following  data:  At  the  larger  mines  of 
Cripple  Creek  the  cost  of  mining  the  total  product  of  ore 
and  waste  is  from  $2.50  to  $3.50  per  ton,  which  includes  all 
the  expenses  of  the  company.  The  above  cost  includes  sort- 
ing the  ore.  The  ore  occurs  in  small  veins,  the  largest  and 
best  of  which  are  in  granite.  In  one  of  the  large  mines  the 
work  done  during  one  month  was  as  follows:  18,910  tons 
were  mined  from  40  different  stopes,  but  including  the  de- 
velopment work  (drifts,  cross-cuts,  etc.)  24,931  tons  were 
mined  at  a  cost  of  $2.55  per  ton,  and  this  was  reduced  by 
sorting  to  7,093  tons  of  shipping  ore,  making  the  cost  $8.96 
per  shipping  ton.  Wages  average  $3.40  for  8  hrs. ;  coal, 
$4.60  per  ton ;  timber,  $20  per  M.  Part  of  the  rock  is  ordi- 
nary, unaltered  granite,  not  excessively  hard,  but  not  soft; 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.    357 

and  part  is  equally  hard  porphyry.    The  costs  in  detail  were 
as  follows: 

c/5  c'  c/r          g  <« 

•     O  M-I                  rj   fj-  en     qj 

£  H  'C  'J3    ^ 

ro   i_  Q            ^   o>  (^   wT 

N  L   |tf  ?I 

oo  -S  g  fe         J  o  S  !> 
Machine  men  and  helpers  and  hand 

miners    $0.34  $1.86      $2.01  $3.16 

Trammers,     shovelers,     pipe     and 

track  men,  etc 0.41  1.03        1.04  0.98 

Timbermen    0.23  1.19 


Total   underground   labor...  $0.98  $2.89  $3.05  $5-33 

Cost  of  machines,  compressed  air, 

drill  sharpening,  repairs,  etc..  0.15  0.97  1.05  1.66 

General  tramming  cost,  repairs  on 

cars,  oil,  supplies,  etc 0.03  0.07  0.09  0.06 

Explosives    0.13  1.43  1.66  1.42 

Lumber  and   timber 0.28  152 

Hoisting  and  tramming  on  sur- 
face    0.23  0.46  0.53  0.40 

General  expense,  bosses,  assaying, 

surveying,  office,  etc 0.23  0.58  0.67  0.45 

Supplies,  miscellaneous    0.04  ....  ....  .... 


Total  cost   $2.07      $6.40      $7.05    $10.84 

In  Mining  and  Scientific  Press,  Feb.  13,  1904,  an  abstract 
is  given  of  the  annual  report  of  Mr.  F.  M.  Kurie,  assistant 
general  manager  of  the  Portland  Gold  Mining  Co.,  Cripple 
Creek,  Col.  The  report  gives  the  following  tables  of  costs 
for  development  work  and  stoping  for  the  year  1903,  which 
is  the  lowest  in  the  history  of  the  company : 

Per  foot. 


19,808    Ft.  Drifts  1,451     Ft.  Raises  Stoping 

Breaking  and    Crosscuts.  and   Winzes.  per    ton. 

Machinemen 

and  miners.  ...  $1.969  $3-458  $0.369 


358        ROCK  EXCAVATION— METHODS  AND  COST. 

Shovelers    ...        $0.038  $0.193  $0.218 

Air  and  air  drills.   1.049  2.02  .179 

Explosives    1.444— $4.50      1.617—  $7.288        i. 39— $0.905 

Tramming — 

Trammers    966  . 883  . 1 75 

Pipe     and     track- 
men     124  .069  .008       * 

General  tramming 

expense    098 —  i .  188       .103 —     1.055         -°34 —     -2I7 

Timbering — 

Timbermen    029  1.503  .215 

Lumber   and    tim- 
bers     017—     .046       -947—    2.45          .310—     .525 

Hoisting    .583  .604  .254 

General   expense  ...  .70  .735  .291 


Total    average 

cost $7.017  $12.132  $2.192 

In  discussing  the  most  economic  methods  of  drifting  and 
stoping  in  the  Cripple  Creek  mines,  Mr.  Victor  G.  Hills 
gives  the  following  data :  Small  drills  are  better  for  drift- 
ing, as  well  as  stoping;  they  are  not  so  fast,  but  take  less 
power.  A  small  compressor  runs  five  2-in.  drills  where 
formerly  it  ran  only  two  3^-in.  drills.  Moreover  the  baby 
drill  is  run  by  one  man  without  a  helper.  A  one-man,  or  baby 
drill,  uses  J^-in.  steel  for  "starters"  and  %  in.  for  long 
drills,  handling  a  drill  8  ft.  long,  although  holes  are  usually 
4  or  5  ft.  deep,  seldom  over  6  ft.  The  baby  drill  is  mounted 
on  a  bar.  One  driller  clears  the  way,  sets  up,  etc.,  and  aver- 
ages 39  ft.  per  8-hr,  shift  in  highly  indurated  andesite  brec- 
cia (hardness,  6  to  7;  sp.  gr.,  2.4  to  2.7).  Machine  men  re- 
ceive $4,  miners  $3  for  8  hrs.  at  Cripple  Creek. 

A  man  driving  a  4  x  7- ft.  cross-cut  puts  in  9  to  12  holes 
for  a  shift.  Records  by  the  month,  without  allowance  for 
sickness,  holidays,  breakdowns,  etc.,  show  a  progress  4.3  to 
4.7  ft.  per  day  of  two  shifts.  A  man  frequently  makes  3  ft. 
a  day  for  several  days.  In  making  an  upraise  4  x  8  ft.  a 
man  averages  2  ft.  a  day,  doing  his  own  temporary  timber- 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     359 

ing;  regular  timber  men  following  10  to  15  ft.  behind,  pro- 
viding a  safe  storing  place. 

In  sinking  a  shaft  8.2  x  17.1  ft.,  depth,  1,000  ft.,  with  no 
water  to  pump,  two  baby  drills  sank  5  ft.  every  2  days ;  the 
machine  men  working  only  12  hrs.  in  every  48  hrs.,  12  hrs. 
being  required  to  muck  and  timber;  5  muckers  worked  one 
shift  to  remove  waste.  This  is  an  excellent  record. 

Confirming  the  foregoing  data  relative  to  the  economy  of 
small  one-man  drills,  a  paper  by  Mr.  B.  L.  Thane  in  Trans. 
Am.  Inst.  Min.  Eng.,  1899,  may  be  cited.  Baby  drills 
mounted  on  tripods  were  used  in  stoping  a  quartz  vein  I  to 
3  ft.  thick.  A  platform  of  lagging  was  laid  on  the  muck 
to  support  the  tripod.  Holes  should  not  be  drilled  more 
than  3  to  6  ft.  deep  to  avoid  sticking  or  binding.  Upon 
striking  a  "slip"  shorten  the  stroke,  loosen  bolts  and  let  drill 
shift  without  stopping.  A  driller  and  a  helper  averaged 
40  ft.  of  hole  between  9  A.  M.  and  4:30  p.  M.,  breaking  twice 
as  much  rock  as  when  using  hand  drills. 

In  drilling  shallow  holes  it  is  especially  desirable  to  re- 
duce the  lost  time  as  much  as  possible.  To  save  time  in 
changing  drill  bits  one  authority  recommends  riveting  the 
two  nuts  on  the  U-bolts.  Cut  a  key  seat  in  the  upper  end, 
and  insert  a  wedge  having  a  small  lug.  Put  in  this  wedge 
with  the  tapering  side  toward  the  end  of  the  chuck  so  that 
every  blow  of  drill  tends  to  tighten  it.  Two  blows  of  a 
hammer  will  loosen  the  wedge  so  that  the  drill  can  be  re- 
moved. 

Cost  of  Drifting  and  Stoping  at  Rossland,  B,  C. — In  a  paper 
entitled  'The  Operation  of  the  'Hole  Contract  System'  in 
the  Center  Star  and  War  Eagle  Mines,  Rossland,  B.  C.," 
by  Carl  R.  Davis,  E.  M.,  read  before  the  American  Institute 
of  Mining  Engineers  the  following  data  were  given : 

The  mines  in  question  contained  a  vein  material  that  was 
exceedingly  variable  in  hardness  and  in  width  of  deposit, 
so  much  so  that  it  was  not  practicable  to  measure  the 
progress  of  a  gang  of  miners  by  the  linear  foot  of  heading 


360        ROCK  EXCAVATION— METHODS  AND  COST. 

or  stope.  An  attempt  was  made  to  keep  account  of  the 
progress  of  each  gang  by  counting  the  car  loads  of  ore  sent 
out,  but  this  had  to  be  abandoned  because  of  the  imprac- 
ticability of  keeping  separate  the  ore  broken  by  each  gang, 
since  the  ore  broken  by  several  gangs  of  men  was  drawn  off 
through  the  same  loading  chute  in  the  mine.  Finally  Mr. 
Davis,  having  observed  that  the  number  of  feet  of  hole 
drilled  (by  two  miners)  with  a  power  drill  did  not  vary 
5  per  cent,  from  month  to  month  (although  it  varied  greatly 
from  day  to  day),  decided  to  introduce  a  system  of  paying 
the  miners  according  to  the  number  of  feet  of  hole  drilled 
each  day.  The  drillers  worked  in  two  8-hour  shifts,  two  men 
to  a  shift,  the  four  miners  thus  forming  a  contract  gang. 
Verbal  contracts  were  made  each  month  with  each  gang  as 
to  price  per  foot  drilled.  No  charge  was  made  for  repairs 
to  tools.  A  blasting  crew  of  a  few  picked  men  worked  from 
I  A.  M.  to  7  A.  M.  while  no  other  miners  were  at  work,  thus 
avoiding  delays  due  to  smoke  accumulations. 

Under  the  old  wage  system  the  miners  received  $3.50  a 
day,  while  under  the  new  "hole  contract  system"  they  earn 
$4  to  $4.25  a  day,  and  the  cost  of  stoping  out  ore  is  about 
48  cts.  per  ton  now,  as  compared  with  86  cts.  under  the  old 
wage  system! 

The  following  tables  give  details  of  cost: 

Comparative  Cost  of  Stoping  Ore. 

f — System — 

Contract  Wage 

(49,849  tons)      (13,818  tons) 
per  ton.  per  ton. 

Drilling     $0.356 


Blasting 021    f  $O75° 

Explosives      .100  .115 


Total  per  ton $0.477  $0.865 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     361 

Cost  of  Driving  Headings. 

Per  lin.  ft. 

Drillins  $5-36  i      $8  6 

Blasting .68  f 

Explosives    2.75  2.78 


Total  per  lin.  ft $8.79  $11.14 

Four  miners  in  drifting  and  cross-cutting  average  per 
month  of  30  days  a  progress  of  97.5  lin.  ft.  under  the  contract 
system,  as  against  50.8  lin.  ft.  under  the  wage  system. 
Twelve  men  (3  shifts)  shaft  sinking  averaged  per  month  58 
lin.  ft.  under  the  contract  system,  as  against  27.2  lin.  ft. 
under  the  wage  system. 

It  will  be  seen  that  the  introduction  of  the  contract  system 
almost  exactly  doubled  the  efficiency  of  the  men,  whether 
they  worked  at  stoping,  drifting  or  sinking,  while  at  the 
same  time  their  daily  pay  was  increased  about  20  per  cent. 
The  figures  are  eloquent  enough  without  further  com- 
ments on  the  advantages  of  the  contract  system  both  to  the 
miners  and  to  the  mine  operators. 

Cost  of  Development  and  Stoping,  Centre  Star  Mine,  B.  C. 
— The  following  data  have  been  abstracted  from  the  recent 
reports  of  Mr.  Edmund  B.  Kirby,  Gen.  Mgr.  Centre  Star 
Mine,  Rossland,  B.  C.  The  main  shaft  sinking  was  done  in 
1901 ;  the  rest  of  the  work  was  done  in  1903. : 
Development  Work. 

Main        Small     Raising.  Drifting.  Stop- 
Shaft.       Shaft.  ing. 

Total  advance,  feet 337          79.         186.      2,903.5       

Ore  stoped,   tons ....         84,453. 

Cost         Cost       Cost        Cost       Cost 
per  ft.        per  ft.      per  ft.      per  ft.    per  ton. 

1.  Drilling $12.95      $6.10      $7.31       $4-53      $0.405 

2.  Blasting    4.89        2.48        2.40         1.08  .03 

3.  Explosives    3.91         3.13        3.72        2.72  .145 

4.  General  mine  supplies.  .2.35  .51  .64  .43  .04 

5.  Mine    lighting — Candles       .62  .26  .19  .14  .015 

6.  "  electric       .72  .30  .22  .13  .01 


362        ROCK  EXCAVATION— METHODS  AND  COST. 

7.  Smithing    $1.09  $1.00  $1.14  $0.72  $0.065 

8.  Tramming    and    shovel- 

ing— direct    19.66  5.51  .65  1.21  .24 

9.  Tramming    and    shovel- 

ing—apportioned   ..1.54  .64  .35           .42  .085 

10.  Timbering — labor    9.60  1.81  3.08           .02  .19 

11.  material  ...     3.16  .33  .57           .01  .11 

12.  Machine     drill     fittings 

and   repairs 1.15  .86  .94          .60  .055 

13.  General  mine  labor....     7.81  1.57  1.18  .84  .09 

14.  Hoisting — underground.  14.28  4-79  •  •  •  •  ....         

15.  main    shaft..     2.19  1.48  .89           .94  .19 

16.  Compressed    air 2.03  1.74  2.08  1.07  .12 

17.  Mine   ventilation 2.29  .23  .17  .13  .015 

18.  Pumping 1.71  1.09  .34    ,  .035 

19.  Assaying 01  .55  .47  .14  .03 

20.  Surveying    59  .20  .17  .11  .01 

21.  General    expense 9.41  3.57  2.71  1.51  .185 


Total    $99.16    $38.77    $29.97     $T7-09      $2.065 

The  raises  and  drifts  are  evidently  large  in  size. 
The  scale  of  wages  is : 

Shift  boss   $5.00       Machinists    $4.00 

Shaft  men 4.00        Blacksmiths   4.00 

Machine  men  3.50        Blacksmiths'  helpers 3.00 

Timber   men $3.00  to    3.50       Hoisting  engineers,  $3.00  to    4.00 

Shovellers   and   car  men..     2.50       Powder  and  tool  boys....     2.50 

Carpenters    3.50       Surface  laborers   2.50 

The  surface  men  work  ten-hour  shifts,  except  carpenters, 
who  work  nine.  On  May  ist,  1899,  the  Provincial  Eight- 
Hour  Law  went  into  effect ;  its  effect  is  to  limit  underground 
work  to  eight  hours.  At  first,  at  the  War  Eagle  Mine,  this 
was  applied  by  putting  on  three  shifts  in  24  hours,  which 
reduced  the  actual  working  time  of  the  men  to  7^  hours, 
as  half  an  hour  was  allowed  for  lunch.  This  was  a  wasteful 
arrangement,  as  in  spite  of  the  blowers  for  forcing  out  the 
smoke  after  blasting,  such  huge  charges  as  were  used  to 
break  the  rock  sometimes  rendered  a  stope  unapproachable 
for  several  hours.  An  air  drill  was  necessarily  often  idle 
also,  to  permit  the  machine  men  to  load,  blast  and  then  clear 
the  muck  away  sufficiently  to  set  up  again. 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.    363 

In  the  spring  of  1900  the  three-shift  system  was  aban- 
doned in  favor  of  the  two-shift,  arranged  thus:  The  first 
shift  started  at  7  A.  M.  and  worked,  with  an  hours'  intermis- 
sion, till  4  P.  M.  ;  the  second  shift  started  at  4  P.  M.  and,  with 
an  hour  for  supper  at  6  P.  M.,  finished  at  I  A.  M.  From  i 
A.  M.  to  7  A.  M.  a  special  blasting  gang  loaded  and  fired  all 
the  ground  drilled  for  breaking.  By  this  method  the  work- 
ing faces  were  freed  from  smoke  before  the  machine  men 
started  work  at  7  A.  M. 

Cost  of  Shaft  Sinking  at  the  Pioneer  Mines. — At  a  recent 
meeting  of  the  Lake  Superior  Mining  Institute,  Mr.  Frank 
Drake  read  a  paper,  giving  in  detail  the  cost  of  lining  a  shaft 
with  steel  as  compared  with  a  timber  lining.  With  steel  at 
2  cts.  per  lb.,  the  cost  of  lining  a  three-compartment  shaft 
with  steel,  was: 

Per  ft.  of 
shaft. 

Steel  in  sets   $4.50 

Labor,   drilling  and   riveting    $1.29 

Iron  bearers,  chairs  and  hangers    0.64 

Wood  lagging   2.12 


Total    $8.55 

With  timber  costing  $14  per  M,  the  estimated  cost  of  lin- 
ing the  same  shaft  was : 

Per  ft.  of  shaft. 

155  ft.  B.  M.,  at  $14  $2.17 

Iron  and  bolts   43 

Labor  framing  sets 32 

150  ft.  B.  M.  2-in.  lagging,  at  $14   2.10 

Labor,  cutting  lagging 27 

Bearers  and  hangers    28 

Total    $5.57 

Mr.  Drake  gives  the  cost  of  shaft  sinking  in  two  shafts 
sunk  at  the  same  time  in  the  same  material,  "Ely  green- 
stone," but,  unfortunately,  one  shaft  was  sunk  by  day  labor, 
while  the  other  was  sunk  by  contract,  which  makes  compari- 


364        ROCK  EXCAVATION— METHODS  AND  COST. 

son  of  little  value.  It  will  be  seen  that  "B"  shaft  required 
about  23  per  cent,  less  excavation  than  No.  2  shaft,  due  en- 
tirely to  the  saving  in  space  effected  by  using  steel. 

C  U  3  f  4- 

OlictlL 

— "B." -No.  2— 

•     .           Pioneer  Mine.  Savoy  Mine. 

Dip    70°  83^° 

Material  of  sets Steel  Wood 

Material    of   lagging Part  wire  rope  Wood 

and  part  wood 

Size  of  Timbers  of  sets 10  x  12  ins. 

Compartments    (2)6  x  6  ft.  and  (2)6  x  6  ft.  and 

(1)5x6  ft.  (1)42-3x6  ft. 

Outside  shaft  dimensions 6l/t  x  18  ft.  7  2-3  x  20  ft. 

Outside  area  117  sq.  ft.  153  sq.  ft. 

Rock  excavated  per  ft.  of  shaft 4  1-3  cu.  yd.  5  2-3  cu.  yd. 

Progress  per  working  day 1.43  ft.  1.54  ft. 

Items  of  Cost  per  Foot 

"B"  shaft         No.  2  shaft 

(steel).  (wood). 

1.  Contract  price  of  excavation $15-95  

2.  Company  labor  account  of  excavation...       5-74  $22.60 

3.  Labor  account  of  lining 2.03  1.45 

4.  Shop  and  team  labor 1.74  2.03 

5.  Explosives   1.86  1.98 

Timber  and  lath  for  sets 5-26 

Mining  timber  1.87  -63 

Iron  and  steel   1.52  1.15 

Steel  rail   4-70  i.io 

Wire  rope  for  lining 37  


Total,  influenced  by  kind  of  lining $35-78 

Other  items  not  influenced  by  kind  of  lining : 
6.     Miscellaneous  labor  regularly  employed*  $10.71 

Pipe  and  fittings 1.17 

Miscellaneous   supplies    4.68 

Fuel    4-30 

Air   2.89 

Temporary  surface   buildings    and   head 
frame    .  28 


7- 
8. 

9- 
10. 
ii. 


•58 


Grand  total   $59-8o 


$52.92 


*  Engineers,  firemen,  landers,  etc. 

N.   B. — Fuel  and  air  items  were  roughly  estimated,  and  are  subject  to  muc 
uncertainty. 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.    365 

Here  we  have  a  comparison  of  cost  very  favorable  to  the 
steel-lined  shaft,  but  it  must  constantly  be  borne  in  mind 
that  the  steel-lined  shaft  was  sunk  by  contract  labor  and  the 
wood-lined  shaft  by  company  labor.  The  "B"  shaft  of  the 
Pioneer  Mine,  Ely,  Minn.,  is  862  ft.  deep,  and  dips  at  an 
angle  of  70°.  The  explosive  used  in  both  shafts  was  40  per 
cent,  dynamite  at  10^  cts.  per  Ib.  Coal  cost  $4  a  ton.  Ma- 
chine men  received  $2.20  and  helpers,  $2.00  a  day. 

Cost  of  Two  Three-Compartment  Shafts. — I  am  indebted 
to  Mr.  Robert  A.  Kenzie  for  the  following  data  on  the  cost 
of  a  three-compartment,  vertical  shaft,  at  the  Helena-Frisco 
Mine,  Frisco,  Idaho: 

COST  PER  FT.  OF  SHAFT. 
Labor.  Supplies. 

Sinking  $28.69       Timbering  $4.64 

Timbering 5.20      Wedges 33 

Shaft  bearers 24      Guides 08 

Hoisting 71       Powder  2.82 

Pumping    44      Fuse 66 

Compressor  engrs 24      Caps   06 

Firing •     .41       Fuel  4.92 

Station  tending 03       Lights 65 

Tool  sharpening 1.13       Tools 56 

Blacksmithing 46       Hanging  irons 58 

General  expense 55       Pump  fittings 42 

.  —  Drill  fittings 46 

Total  for  labor $43.10       Lubricants    26 


Total  for  supplies. ..  .$16.42 

This  shaft  was  sunk  from  the  6oo-ft.  level  to  the  1, 600- ft. 
level,  1,000  ft.,  in  516  days,  at  a  cost  of  $59.52  per  ft.  for 
labor,  materials  and  supplies.  The  200  ft.  between  the  600 
ft.  and  the  800  ft.  level,  were  sunk  in  81  days,  at  a  cost  of 
$49.68  per  ft.  for  labor,  and  $16.71  for  supplies.  Unfortu- 
nately at  the  time  of  going  to  press  I  have  not  received  the 
rate  of  wages  and  prices  paid. 

In  the  School  of  Mines  Quarterly,  1904,  Mr.  R.  A.  Parker 
gives  the  following  data  on  the  sinking  of  a  shaft  at  the 
Hamilton-Ludington  Mine,  Iron  Mountain,  Mich.  The 


366        ROCK  EXCAVATION— METHODS  AND  COST. 

shaft  is  7  x  21 J4  ft.  in  the  clear;  9^  x  24  ft.  being  the  aver- 
age area  excavated,  and  is  1,400  ft.  deep  in  a  uniform  dolo- 
mite that  drills  and  breaks  readily.  Two  shifts  were  worked 
requiring  a  total  of  37  men,  including  surface  men.  The 
best  month's  progress  was  90  ft.  The  center  cut  holes  were 
9  ft.  deep;  the  second  set,  3  ft.  back,  8  ft.  deep  and  more 
nearly  vertical;  the  third  set,  3  ft.  back  of  the  second, 
7  ft.  deep,  and  the  remaining  holes  squared  up.  The  total 
number  of  holes  was  32.  The  advance  at  each  blast  was  5 
ft.,  200  Ibs.  of  45  per  cent,  dynamite  being  used  in  a  blast,  the 
cut  holes  charged  one-third  heavier  than  the  others. 

Cost  of  Mining,  Douglas  Island,  Alaska. — For  the  follow- 
ing data  I  am  indebted  to  Mr.  Robert  A.  Kinzie,  Asst.  Supt. 
Treadwell  Mines,  and  to  an  excellent  paper  by  him  in  the 
Trans.  Am.  Inst.  Min.  Eng.,  1903. 

The  ore  is  a  mineralized  syenite  having  a  specific  gravity 
of  2.61  at  the  Ready  Bullion  Mine,  2.64  at  the  Mexican 
Mine,  and  2.67  at  the  Treadwell  and  7oo-Foot  Mines.  The 
country  rock  is  a  slate.  No  timbering  is  used  in  the  stopes, 
where  the  ore  is  shot  down  in  large,  thin  slabs,  so  that  the 
fall  will  break  it  as  much  as  possible.  In  stoping,  the  drill 
holes  average  8  ft.  deep;  a  (3^  to  3^-in.)  drill  averaging 
28.7  ft.  of  hole  per  lo-hr.  shift,  breaking  down  35  tons  of 
ore  with  a  consumption  of  12^  Ibs.  of  40  per  cent,  dynamite. 
The  cost  of  breaking  the  ore  after  it  has  been  blasted  is  a 
large  item  of  expense,  as  one  man  takes  one  day  to 
sledge  and  bulldoze  35  tons  of  ore,  using  0.85  Ib.  of  70  per 
cent,  dynamite  for  bulldozing  each  ton  of  rock.  A  stope  is 
usually  7  ft.  high,  150  to  300  ft.  long,  and  of  variable  width ; 
the  floor  of  a  stope  slopes  from  the  parallel  lines  of  chutes  at 
an  angle  of  30° . 

Drifts  and  cross-cuts  are  usually  7  x  10  ft.  in  the  clear, 
and  raises  are  6  x  8  ft.  in  the  clear,  no  timber  being  used. 
The  rock  has  no  seams  or  slips  to  break  to,  making  it  difficult 
to  break  to  the  bottom  of  holes.  In  drifting,  6  cut  holes,  6 
ft.  deep,  converging  toward  a  point,  are  drilled ;  4  relievers. 


-   COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.     367 

5  ft.  deep,  are  next  drilled  with  a  slight  rake  toward  the 
center;  finally,  12  trimmers,  5  ft.  deep,  are  drilled  around 
the  floor,  sides,  and  top  of  the  drift.  The  cut  holes  are 
blasted  with  70  per  cent,  dynamite ;  the  rest  with  40  per  cent. 
The  price  of  the  40  per  cent,  powder  is  about  14%  cts.  per 
Ib. 

At  each  level  a  station  is  cut  the  width  of  the  shaft, 
50  ft.  long,  and  8  ft.  high ;  beneath  the  floor  of  each  station 
an  ore  bin  is  cut  out  so  as  to  give  a  storage  capacity  of 
500  to  1,500  tons  of  ore.  The  ore  is  trammed  from  bins 
at  the  bottom  of  stopes  to  the  storage  bins  at  the  shaft, 
drawn  off  into  skips  and  hoisted  to  the  surface.  Tramming 
is  done  by  hand,  by  horses  and  by  the  tail  rope  system. 

About  58  per  cent,  of  the  total  ore  excavated  is  taken 
from  open  pits,  the  largest  of  which  has  now  reached  a 
depth  of  450  ft.,  and  has  a  maximum  length  of  1,700  ft.  and 
a  width  of  420  ft.  When  a  pit  is  opened,  a  raise  is  put  up 
from  the  nearest  level  to  the  surface,  and  all  the  ore  ex- 
cavated in  the  pit  is  shot  down  this  raise  into  a  chute  from 
which  it  is  trammed  to  a  bin  at  the  shaft,  and  hoisted  in 
skips.  The  spacing  of  the  holes  in  this  pit  work  is  given 
on  page  216. 

The  duty  of  drills  and  of  explosives  in  the  different 
class  of  work  is  as  follows : 


Per  drill  pei 
lo-hr.  shift. 

^  B 

g  B 

$Z 

Ft.  of  drill 

Tons  of  ore 

°    o3    • 

A  ? 

Open   Pits 
Stopes     .  .  , 

hole 
....   37.4 
^o.o 

broken 
69.7 

35-7 
11.7 

94 

fa    a 
0-54 

345 

2.00 

0.23 

1.40 
1.50 
1.40 

Drifts    ... 

....    36.8 

Raises   ... 

.    ^2.4 

Shaftsf   .  .  . 

,    32.8 

*  This   includes   only   the  dynamite  used   in   drill   holes,  and   does   not   include 
dynamite   used    in   bull-dozing, 
"t  Three  of  the  shafts  are  three-compartment,  and  one  is   four-compartment. 


368        ROCK  EXCAVATION— METHODS  AND  COST. 

The  cost  operating  each  drill  per  lo-hr.  shift  is  as  follows: 

Labor $7.58 

Drill  sharpening,  repairs,  power,  etc 2.42 


Total $9.00 

The  cost  of  power  is  low,  for  about  80  per  cent,  of  the  year 
water  power  is  used  to  run  to  the  compressors.  On  the 
other  hand  wages  are  fairly  high,  being  as  follows  per 
ic-hr.  shift: 

Machine  drillers,  $2.50  to  $3  with  board  and  lodging, 
helpers,    $2.25  "     .    " 

Mine    laborers,      $2.00 

Blacksmiths,  $4.00 

Tool-sharpeners     $3.50 

The  Treadwell  group  of  mines  is  justly  celebrated  for 
the  fact  that  gold  ore  having  a  value  of  less  than  $2  a  ton 
is  mined  and  milled  at  a  profit.  The  following  table  gives 
the  itemized  cost  of  mining  a  ton  of  ore  at  each  of  three 
mines,  the  output  being  that  of  12  months,  1901-2.  The 
low  cost  of  the  Treadwell  mine  is  due  not  only  to  the  fact 
that  larger  quantities  of  ore  were  handled,  but  to  the  fact 
that  most  of  the  pit  mined  ore  was  taken  from  the  Tread- 
well.  In  considering  the  following  data,  it  should  be  re- 
membered that  the  ore  deposit  is  massive,  that  there  is  no 
timbering,  and  very  little  pumping.  The  cost,  low  as  it  is, 
could  have  been  still  further  reduced  had  crushers  been  in- 
stalled capable  of  receiving  rocks  18  x  36  ins.  in  size,  thus 
reducing  the  cost  of  bulldozing. 

COST   OF   ORE   PER  TON. 


.  .  •  C 

c«  en  '       cfl  O 

C  G  C  ;- 

•     O  O  P  ~ 


$  rt    in         M 


10  CM    W 

01 

m   >> 


Tool  sharpening,  labor    $0.0191    $0.0322    $0.0400 

"  supplies    0048        .0057         .0107 


COST  OF  DRIFTING,  SHAFT  SINKING,  STOPING.  369 

Machine  drilling,  labor    $0.2280    $0.2720  $0.2521 

"        merchandise    0050  .0058  .0015 

"        steel    0192  .0209  .0159 

Compressed  air,  labor    0032  .0031  .0029 

"     steam     0293  .0572  .0882 

"     supplies    0082  . 0245  . 0064 

Explosives,  fuse    0030  . 0028  . 0027 

caps    0018  .0012  .0012 

70%    dynamite 0079  .0175  .0154 

40%    dynamite 0656  .0822  .0709 

labor  on  primers 0042  .0056  .0063 

Rock  breaking,  labor    1643  .2137  .1439 

supplies     0037  .0037  .0041 

fuse    0070  .0067  .0064 

caps   0042  .0029  . 0029 

70%    dynamite 1233  .0916  .0874 

labor  on  powder 0099  .0132  .0148 

Tramming,  labor   0262  .0185  .0325 

horses  0042  . 0023        

supplies   0055  .0066  .0005 

Hoisting,  labor  0170  0.448  .0194 

supplies    0023  .0014  .0048 

steam    power 0293  .0572  .0882 

Illuminants    0085  .0149  .0104 

Supplies,  iron  and  foundry 0201  .0350  .0578 

Repairs    0080  .0102  .0057 

Assaying   0015  .0027  .0024 

Personal    0039  

General    .                    0017  .0029        


Total    $0.8399    $1-0590    $0.9954 


INDEX. 


PAGE 

Abel   block    138 

Absorbent 114 

Adit     341 

(See   also    Drift;    Tunnel) 
Air: 

Flow   in    pipes    63,   64,   65 

Table   of  H.   P.   to  compress..        50 

Merits    of    compressed     68 

Work    of    compressing     49 

Compressor,   cost    87,  88 

Gasoline ;  o 

Tests    59,  69 

Air    Drill.    /See   Drill.) 

Hoist 243 

Asbestos    60 

"Baby  drill"    (see    Drill,   baby) 

Backs    5 

Bank    blasting 158 

Battery,    electric 133 

Belt    conveyor 310 

Bench    214,   297 

Bent    297 

Bit.      (See    Drill-bit.) 
Black    powder.       (See    Powder.) 
Blacksmithing.      (See   Drill — bit-sharp- 
ening.) 

Blasting    1 24,    141 

Bank    158 

Boulders.       (See    Boulders.) 

Close    to    Buildings    192 

Gravel    157 

Hardpan    157,    239 

Ice    162 

In   seams' 206 

Knox    system    197,    199,    210 

Piles     160 

Stumps     .  . 160 

Subaqueous     278 

With  powder  and  dynamite  to- 
gether           169 

With    water    cushion 204 

Blasting-  gelatiin     f2i 

Blasting-mat     269 


PAGE 

Blasts,   large   chamber 150 

Block-holing   162 

Block   quarry    187 

Boiler,     efficiency 65 

Borts    95 

Boulders,  blasting   ..162,  233,  235,  366 

Dredging     295 

Sledging     232 

Breast    34i 

Brick    tunnel    lining    338,    340 

Broaching 192 

Broken    stone,    voids    9 

Loading    165 

(See    also    Loading.) 

Buffalo    breakwater    198 

Bucket,   clamshell    166 

Bull-dozing.      (See    Mud-capping.) 

Bull-points    ^68 

Bullying.        (See      Drill-hole,       spring- 
ing.) 

Cableways 153,    164,    244,    248,   273 

Canal,    Chicago    aj8 

Cantilever   crane    250,    255,    257 

Caps   128,   136,  137 

Carbons     95 

Cars,    hauling   in 

165,    171,    182,    226,    241,    244,    355 

Car-hoists     258 

Carts,    hauling   in 177,    180,    226 

Cat    holes    35 

Center-cut     297 

Chamber    blasts    150 

Chambering.      (See    Drill-hole    sprftig- 
ing.) 

Channeling 105,    193,   261  to  264 

Charging   explosives    ...124,   269,    286 

Chicago    canal     238 

Churn-drill.      (See    Drilling,    hand.) 

Chuck     31 

Chuck  tending    17,   37 

Clamshell    bucket    166 

Clay    excavation    239 

Coal.      (See    Fuel.) 


372 


INDEX. 


PAGE 

Column    for    drill     40 

Compressed    air.       (See    Air.) 
Concrete.      (See    Tunnel    lining.) 

Drilling    44 

Contractors  powder    122 

Conveyor    belt     310 

Crane.       (See    Cantilever    crane; 
Locomotive   crane.) 

Crater   theory    142 

Crimper    1 28 

Cross-cutting.  .341,    349,     356    to    .558 
Crushed   stone.      (See    Broken    stone; 
see   Crushing.) 

Crushing    217,    220 

Cut-holes    297,  301 

Cutters     5 

Depreciation     86 

Derby  bit    290 

Derrick 166,    180,    196,    206 

Double  boom    254 

Hullett-McMyler    252 

Derrick-car    231,    236 

Derrick-scow    279,    283,    284 

Detonators    132,    139 

Development  work    241 

Devil    -236 

Diamond   drilling    95   to   97 

Dimension  stone    184 

"Dinkey"    locomotive    174 

Dip    5,    185 

"Dolly"    29 

"Dope"    in 

Dredging 

278,  281,   286,  287,   290,   292,    204 

Dressing.      (See    Trimming.) 

Drifting.  ...  139,    152,    158,    289,    341, 

349,    354,   357,    358,   361,   366,    367 

Drill,   air   required    ....51,   55,   56,   57 

"Baby"    191,  222,  223,  358,  359 

Bar  mounting   40,  354 

Brandt  rotary   -.  .  .45,  333 

Care  of   37 

Coal    consumption.      (See    Fuel.) 


PACK 

Column     40 

Depreciation    86 

Diamond    95   to  g~ 

Electric    46,    93 

Gasoline     46 

Hand    13 

Handling  a    34 

H.    P 56 

Leyner   45,   55,  83,  351 

Mechanism    31 

Price   of    34,    86 

Repairs  86,  221,  223,   311,   344,   362 

Rand    53,    54 

Sizes    of    32,    56 

Steam  consumption   58,  67 

Table  of  data    34 

Tests    52,   78 

Well   90,   215 

(See  also  Drill-bit;   Drill-holes;  and 

Drilling.) 

Drill-bit,    Brunton    26 

Derby     290 

Fitch    26 

Hand  drills 15,  17,  23  to  25 

Sharpening,   26  to  30,  85,   201,  209, 

211,  213,  219,  223,  274,  285,  286, 

311,  314,  322,  329,  334,  362,  365, 

368 

Tubular   290 

Wear   of    24,    329,    347 

Drill-holes,  cost  of  charging.  . . .      220 

Depth  of   economic    215 

Size  of  15,  23 

Spacing,    144,    146,    215,    216,    250, 

286 

Springing    147,   216,  268,   302 

Drill-platform 288,    293,    296 

Drill-scow    278,   285,  29'2,   294 

Drilling,  churn.     (See  Drilling,  hand.) 

Contest    52,    78 

Contract   system    360 

Cost  of  hand.      (See  Drilling,   hand 

work  * 


INDEX. 


373 


PAGE 

Cost    of    machine.  .21,    72,    92,    94 

213,  219,  222,  223,  247,  248,  261, 
265,   270,    275,   368 
Effect    of   air    pressure,    52,    55,   83, 
352 

Direction  of  hole...  15,   16,  347 

Shallow    holes 81,  223 

Size  of  hole 54,   342 

Sludge    16 

Footage,   52,   79,   84,   193,   202,  223, 

300,    319,    321,    331,    334,    345,  366, 

367 

Hand  work,    15   to  22,  (&^)  272,  313, 

316,    332 

Plug-holes,    20,    45,     163,     187,  189 

Rates    in    different    rocks 82 

Rule   for  estimating   footage..  79 

Drilling,   subaqueous,  281,    285,  287, 
288,    292,   294,   295 

Table  of   average  time 77 

feet    per    cubic    yard,    217,  237 

Time  to  change  bits 73,  359 

Shift    drills    75 

Use   of   water   in,    16,    38,    42,  55, 

83,  291,  347 
(See  also  Drill.) 
Dump  car.  (See  Car.) 

Dynamite 106,    no,     in,  114 

Accidents    n  7 

Charging     124,  127 

Effect    on    stone    124 

Fumes    130 

Grade  to   use    125,  365 

Leaking    118 

Testing    121,  138 

Thawing    116,  118 

Weight     115 

Earth  excavation    157,   228,  239 

Electric    battery 131,  133 

Detonator.      (See    Detonator.) 

Drilling 46,    93 

Engine.      (See  Steam  Engine.) 

Excavation,    Chicago    canal 261 


PAGE 

Classification     226 

Clay     239,    306 

Earth     228 

Gneiss     222 

Hardpan 157,  239 

Loose    rock    228 

Open-cut,     16,     214,    261,    275,    338 

Sandstone 223,    225 

Shale     224 

Subaqueous   131,  277 

Table   of    drilling   and    explos- 

sives    237 

Expansion    tamping    127 

Exploders.      (See    Caps,    Detonators.) 

Explosives   106,  237 

Kind    to    use 124 

(See       Dynamite,       Joveite,     Judson, 

Powder,   etc.) 
Feathers.      (See    Plug   and    Feathers.) 

Feed-screw     32 

Fire  clay 306 

Firing    131,    136 

(See    Blasting.) 

Fitch    bit    26 

Flatter     29 

Forceite     113 

Free-air     49 

Fuel,  65,  67,  70,  89,  90,  92,  209,  221, 
223,  322,  323,  349 

Fuse     136 

Fuse-cutter 129 

Gadder    192 

Gas.      (See     Ventilation;     see     Explo- 
sives.) 

Gasoline    drill    46 

Gelatin    121 

Giant  powder 112 

Go-devil    310,    316,   324 

Grain    • 185 

Granite    7,   204,   207 

Gravel,    blasting    157 

Hardpan,  blasting 157,   239 

Hauling.     (See  Cars,  Carts,  Wagons.) 


374 


INDEX. 


PAGE 

"Head"    185 

Heading   297 

Heat  energy 47 

Hoist    243,   258,  285 

Hole.      (See  Drill-hole.) 

Horse-power 47,    48,    66 

Hydraulic    hoist    285 

Ice  blasting    162 

Igneous   rocks    4 

Inclines   241  to  244,  341 

Insulating  tape    132 

Interest  and  depreciation    86 

Iron    ore   mining    168,    173,    221 

Joints   in    rock 4,    184,    186 

Joveite 106,    122,    131,    135,    218 

Judson   powder.  ...  106,    122,    124,    131 

Jumbo    324 

Knox  holes 197,    199,    210 

Lagging    297 

Level    341 

Lewis   hole 205 

Lift    214 

Limestone    6 

Line  of   least  resistance 142 

Lining.       (See     Tunnel     lining.) 

Lizard    ^35 

Loading    rock,    by    drag    scraper     325 
By   hand,    164,    220,   254,    255,    257, 

262,    321,    322 

By     steam     shovel.        (See     Steam 
Shovel.) 

Locomotives    1 74 

Locomotive-crane    250,    253 

Machine   drills.      (See    Drill.) 
Masonry,   186,  203,  211,  212,  317,   329 
(See   also    Tunnel   lining.) 

Mat   269 

Measuring    rock    1 1 

Metamorphic    rock    4 

Minerals,    rock-forming    i 

Mining,   pit 217,    221,   367 

(See    Stoping.) 
Misfires   I34)  200 


PAGE 

Muck    298 

Mucker    326 

Mud    26 

Mud-capping 162,    233,    235,    366 

Neat  lines    12,  267 

Nipper    300 

Nitroglycerin    no 

One-man   drill.      (See    Drill,    "Baby.") 
Open-cut.      (See    Excavation.) 

Over  burden    214 

Packing   305 

Pile    blasting    160 

Pipe.      (See    Air;    Steam   Pipe.) 

Plank  road    180 

Plant  rental    86 

Steam    and   air    47 

Plug  and  feathers 20,    187 

Plug-drills 45,    163,    189 

Pneumatic      plug-drill.        (See      Plug- 
drill.) 

Porphyry    7 

Pound-degree    48 

Powder    106,    ic8,   109 

Charging 124,  269,   286 

Weight 109 

Primer 128 

Quarry    bar    191 

Quarrying    16,    184,    339 

Boulder   208 

Gneiss    210 

Granite    204,    207 

Limestone    212,   220 

Sandstone    203,   211 

Trap    218,  219 

(See    Excavation.) 

Rackarock    289 

Railway  tunnel.      (See   Tunnel.) 

Raising 341,    357,    358,    361,    367 

Rapid   transit   subway    273 

Re-heater    195 

RentaJ,    plant     86 

Rift    184 

Rigger    246 


INDEX. 


375 


PAGE 

Rip-rap    12 

Road,  plank    180 

Rock  coefficient    144 

Denned    226 

Drill.      (See    Drill.) 

Species    3 

Safety  fuse 136 

Sandstone   6,  203,  2 1 1 

Scaffold   car.      (See    "Go-devil.") 
Scale-pan.      (See   Skip.) 

Scows,  measuring  in    199 

Sedimentary  rock    3 

Shaft  sinking,   156,  318,  341,  342,  343, 
347,   353,  359,   361,    363,   365,    '567 
Shaking.        (See     Drill-holes,     spring- 
ing.) 

Shale 6,   224,   310,   313 

Sharpening.      (See    Drill-bit,    sharpen- 
ing.) 

Sheet   quarry    187 

Shoveling.   (See  Loading  Rock;  Steam 

Shovel,) 
Sinking.     (See  Shaft  Sinking.) 

Skid  road   181 

Skip   164,  246,  252 

Sled.     (See  Stone  boat.) 

Sledging 220,  223,  233 

Slides    12,   230 

Sludge 17,  38 

Snatch  team iKo 

Specific  gravity 8,  10 

Soda  powder.     (See  Powder.) 

Spoon J7 

Spreader    29 

Springing  drill-holes.    (See  Drill-holes, 
springing.) 

Steam   Boiler,   efficiency    65 

Steam   Drill.      (See   Drill.) 

Steam  Engine,  efficiency 48 

Steam  pipe,  area  of   62 

Covering 61,  326 

Efficiency    60 

Steam,  table   50 


PAGE 

Steam  shovel,  fuel  for 174 

Tunnel  work 300,  306 

Work,   1 68,  216,  224,   236,  239,   240, 
242,  266 

Steel  trackway 180 

Weight  of 19 

Stone-boats   180,  235,  308 

Stone  cutting,  cost   339 

Dimension 184 

Racks    178 

Trucks 180 

Sloping,   341,  346,   356,  357,  360,  361, 
366,    367 

Strike 5 

Stripping    214 

Stump  blasting 160 

Subaqueous  excavation 131,  277 

Subway,  N.  Y 273 

Swage ~9 

Tamping 108,   126,    130 

Cushion   135 

Expansion    127 

Water   U* 

Tape U2 

Thawing  dynamite 1 16,  118 

Timbering 305,  3*3,  3*6,  326 

Tipple   243 

Ton   ii 

Track   channeler.       (See  Channeling.) 

Track,  layout 182 

Trackway,  steel   180 

Traction  engine 180,  328 

Trap 8,  218,  219 

Trenching    206,   230,   267,  270 

Trimming  slopes 228 

Tunnel,  American 297 

Blasting  in    132 

Busk    327 

Carr's    338 

Cascade    307,  323 

Croton 318 

Gallitzin   299 

Glasgow 21 


376 


INDEX. 


PAGE 

Hogsback  mine 345 

Hoosac   21,  23,  297 

Kellogg 325 

Melones  mine 343 

Mount  Wood   3 1 3 

Mullan    339 

Musconetcong 329 

Nesquehoning     21 

New  Croton   318 

Newhouse    350 

Peekskill    336 

Pryor  Gap 326 

Simplon 298,  332 

Stampede   307 

Sutro    328 

Tequixqueac    331 

Top  Mill    313 

Wabash    302 

(See    also    Drifting.) 


PAGE 

Tunnels,    lining,    297,    305,    310,     317, 
324,  328,   337,   338,  340 

Steel  centers  for  lining 333 

Use  of  traction   engine  in 328 

Ventilating,  299,  326,  328,  331,  336, 
343.   3Si,   352 

Twin-headings    303 

U-bolt 31 

Upraise.      (See  Raising.) 
Ventilation.       (See    Tunnels,    ventiiat- 
ing.) 

Voids   8,  9 

Wagons,  hauling  in 177,   179 

Wall-plates 300,  302 

Water  telescope 199 

Weight   of   rock    8,    10 

Well-drillers,   cost  by    90,   215 

Wheelbarrows,  cost  by 176 

Wiper 126 


ADVERTISEMENTS. 


INGERSOLL=SERGEANT 

ROCK  DRILLS 


AND 


ADR 
COMPRESSORS 


For  every  condition  of 


{Tunneling 
Excavating 


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CO, 

26  Cortlandt  Street 

Cleveland,  O.  Boston.  Mas*. 

Chicago,  111.  NEW  YORK      Philadelphia,  Pa. 

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ADVERTISEMENTS. 


COM- 
PRESSORS 


'ROCK 
DRILLS 


RAND  DRILLS 

"  Drilled  good  round  hole. 
No  stop  from  drill  stick- 
ing." 

'  Most  satisfactory  runs. 
Rotation  pood.  Holes  per- 
fectly round.  No  stops  from 
drills  sticking  and  no  hitch 
of  any  kind." 

"Thoroughly  good  run. 
No  stop." 

'•'Machine  taken  direct 
from  box  and  put  on  bar. 
Rather  stiff  at  starting. 
Rotation  good  and  hole 
round." 


OTHER  MAKES 

"  Stroke  very  erratic.  The 
machine  occasionally  mak- 
ing a  stroke  without  strik- 
ing a  blow." 

"Rotation  bad  and  hole 
rifled.  Considerable  lessen- 
ing of  speed  of  machine." 

"  Stoppage  due  to  mechan- 
ical defects.  Backhead 
loose;  bolts  bent  when 
tightening  up.  Machine 
was  not  tried  below  60  Ibs." 


Which  do  you  want  ? 


RAND  DRILL  (Q. 


EXTRACT  FROM  REPORT  OF  TEST 

of  Rock  Drills  Recently  Held  at  City  &  Suburban  Q.  M.  Co.       m 
Johannesburg,  South  Africa 

EXTRACTS   FROM  REPORT 


128 
BROADWSY 


ADVERTISEMENTS.  iii 

THE  "PIERCE"  CORE  DRILLS 

Are  the   Best  and  Cheapest  for  Making: 
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Member  of  The  American  Society  of  Mechanical  Engineers 

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pines.  24  were  used  by  the  Nicaragua  Canal  Commission  in  making  20OO  Test 
Borings  for  the  Nicaragua  Canal.  Thpy  are  now  being  used  by  the  Isthmian 
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other  Governments.  Extensively  used  by  engineers  and  contractors  for  the 
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iv 


ADVERTISEMENTS. 


Mailed  free 
with  others  on 

Elevating 
Convening 
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Catalogue  67  A 
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THE  SIMPLICITY  OF 
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IRocfc 


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MAINTENANCE 

Drill  Catalogue  No.  76 


THE  JEFFREY  MFG.  CO. 


PITTSBURG 


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ADVERTISEMENTS. 


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HAVE  BEEN  USED  FOR  OVER  IO  YEARS  IN    HANDLING 

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THEY  ARE  THE  FIRST  AND  BEST 

The  life  of  a  belt  is  from  4  to  8  vears  according  to 
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vi  ADVERTISEMENTS. 


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TROY  PUBLIC  WORKS  COMPANY 

R.  W.  SHERMAN,  President,  Utica,  N.  Y. 


ADVERTISEMENTS. 


vii 


ESTA  BUSHED      I6S7 


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viii  ADVERTISEMENTS. 

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HOISTING 
ENGINES 

OVER 

23,000 


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SEND  FOB  LATEST  CATALOGUE 


LIDGERWOOD   MFG.  CO, 

96  Liberty  Street,  NEW  YORK 


ADVERTISEMENTS.  ix 


ftbe 

Engineering 

IRecorb 


The  Leading  Publication 
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x  ADVERTISEMENTS. 

M.  L.  WYATT  &   COMPANY 

SALISBURY,    N.   C. 

Granite,  Limestone,  Marble 

GRANITE  MILLSTONES   A   SPECIALTY 


MINING  AND  TIMBER   LAND    BOUGHT  AND   SOLD 

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MANUFACTURERS  OF 


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anb  Electrical 


The  CALIFORNIA  CAP  is  universally  recognized 
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can  compare  with  it. 


xi 


ADVERTISEMENTS. 

2)nllin0  flfoacbines 

For  MAKING  LARGE  AND  DEEP  BLAST  HOLES.  Pulverizing 

Material  ahead  of  Steam  Shovels  in  heavy  Railroad  Cuts,  Street  Grading, 
Canals,  Etc. 

EXPLORING  SUBWAYS  AND  TUNNELS.  Drilling  and  Casing  Air 

Holes,  and  Pumping  Shafts 
for  Mines  and  Tunnels. 

Making  Soundings  for 
Bridge  Piers,  and  Under- 
Rivar  Tunnels.  Usable  on 
Flatboats 

Making    Holes   for  Hy- 
draulic Elevators,  Etc. 

Machines  are  moved  from 
hole  to  hole  by  their  own 
p«>wer  without  taking  down 
the  mast.  By  their  use  the 
powder  is  bunched  at  the 
bottom  of  the  excavation. 

SEND  FOR  OUR  SPECIAL  CIRCULAR. 

We  cover  the  whole  field.  Catalog  No.  1  describes  Water- Well  Machines. 
Catalog  No.  2,  Mineral  and  Placer  «io'd  Prospectors.  Catalog  N«-.  3,  Portable 
Oil-Well  RitJS.  Ea--h  catalog  contains  a  valuable  rti-cussion  of  the  line  of  work 
to  which  it  relates,  and  the  best  methods  of  doing  it.  Catalog*  free. 

The  Keystone  Driller  Co.,  Beaver  Falls,  Pa.,  U.  S.  A. 


3>allett 
Plug  3) rills 

The  prominent  features  of  our  latest  type  are: 

Moderate  first  cost— Economy  in  use  of  air. 

Least  possible  recoil  or  vibration  and  the  rendering  of  repairs 

inexpensive  when  necessary. 

The  barrel  of  this  drill  is  provided  with  an  inner  removable  lining,  so  that 
when  after  long  service  they  becom^  worn,  this  lining  can  be  removed  and  a  new 
one  pressed  in  ar.  H  slight  expense,  practically  renewing  the  tool  and  prolonging 
its  life  indefinitely. 

THOS.  H.  DALLETT  CO. 

York  St.  and  Sedgely  A ve.,  Philadelphia,  P?. 
Chicago,  Cleveland,  Cincinnati,  San  Francisco,  Boston,  Pittsburg,  Barre,  Vt. 


xii 


ADVERTISEMENTS. 

THE 


Economy  Blast  Mole  %oaber 


704  feet  of  drilling: ;  $37.00  in  Powder  is  the  saving 
we  made  in  a  single  shot  by  the  use  of  the  "  Economy." 
This  Loader  saves  Dollars  in  Powder,  Time  and  Worry. 

Write  to-day  for  our  Booklet,  "The  Economy  Blast 
Loading  System." 


COPE  &  CORNELIUS 

ORRVILLE,  OHIO 


ADVERTISEMENTS.  xiii 

BLAST  HOLE  DRILLS 


Cyclone  Drilling  Machines 

Built  and  Equipped  with  special  outfit  of  tools  to 
meet  every  requirement  of  the  Contractor.  To  drill 
blast  holes  in  any  and  all  formations  with  safety,  at 
the  minimum  of  cost  and  the  maximum  of  speed.  The 
First  Practical  Drill  for  drilling-  3-inch  holes. 


SEND  FOR  OUR  CONTRACTORS'  CATALOGUE 


The  Cyclone  Drilling  Machine  Co< 


ORRVILLE,  OHIO 


xiv  ADVERTISEMENTS. 

THE   LARGEST   MANUFACTURERS   OF 

Explosives 

IN   THE   WORLD 

Dynamite 

Fumeless  Gelatine 

Black  Powder 

(For  Blasting) 

WRITE  FOB  CATALOGUE  ON    EXPLOSIVES 


E  L  DUPONT  COMPANY 

WILMINGTON,  DELAWARE 

The  Watt  Mining  Car  Wheel  Co. 

BARNESVILLE,  OHIO 


flIMne  ant>  ©re  Cars  of  Ever?  Inscription 

SPECIAL    CARS    FOR    ROCK    WORK 
'• WRITE  US  FOR  ESTIMATES 


A  D  VER  TI  SEMEN  TS.  xv 


JOVEITE 


FEATURES: 

1.  Strongf  as  dynamite — grade  for  grade. 

2.  Comes    in    sticks ;    is    loaded    and   fired   like 

dynamite. 

3.  Is  a  dry,  free-running-   powder,  and  does  not 

freeze. 

4.  In  six  years  of   use  not  an  accident   has  oc- 

cured  to  a  user. 

5.  Neither  heat  nor  cold  affects  it;  equally  good 

in   the   torrid,  the   frigid  or  the   temperate 
zone. 


The  Explosives  Mfg,  Co, 

320  BROADWAY,  NEW  YORK 


xvi  ADVERTISEMENTS. 

JOHN  WILEY  &  SONS' 

Scientific  publications 

Baker*     A  Treatise  on  Roads  and  Pavements 

8vo,  viii+6f  5  pages,  171  figures,  68  tables.    Cloth,  $5.00. 

Baker*     A  Treatise  on  Masonry  Construction 

8vo,  about  600  pages,  160  figures  and  6  folding  plates.    Cloth,  $5.00. 

Drinker*     Tunneling,    Explosive    Compounds,  and     Rock 
Drills 

4to,  x+1,175  pages.     Profiles,  Maps,  and  over  1,000  illustrations. 
Half  morocco,  $25.00  net. 

Eissler*     The  Modern  High  Explosives 

8vo,  xi+395  pages,  129  figures.    Cloth,  $4.00. 

Mutton*     The  Mechanical  Engineering  of  Power  Plants 

8vo,  xxviii+725  pages,  510  figures.    Cloth,  $5.00. 

Ihlseng*     A  Manual  of  Mining 

8vo,  xxii+563  pages,  262  figures.    Cloth,  $4.00. 

Kent.     The  Mechanical  Engineers9  Pockct=Book 

16mo.  xxxii +1,113  pages,  illustrated.    Morocco,  $5.00. 

Merrill.     Stones  for  Building  and  Decoration 

8vo,  x+557  pages,  one  double-page  and  32  full-page  plates,  and  24 
figures  in  text.    Cloth.  $5.00. 

Molitor — Beard.     Manual  for  Resident  Engineers  Contain- 
ing General  Information  on  Construction 

16mo,  iv+118  pages.    Cloth,  $1.00. 

Richards.     Compressed  Air 

12mo.  v+203  pages,  illustrated.    Cloth,  $1.50. 

Taylor — Thompson.     A  Treatise  on  Concrete*  Plain   and 
Reinforced 

8vo,  many  illustrations,  400  to  500  pages.    Keady  October  15, 1904. 

Walke.     Lectures  on  Explosives 

8vo,  xvi+435  pages.    Cloth,  $4.00  net. 

Webb.     Railroad  Construction 

16mo,  xvi+675  pages,  216  figures.  10  plates.    Morocco.  $5.00. 


Descriptive  Circulars  and  Catalogues  on  Application 

43  AND  45  EAST  19th  STREET,  NEW  YORK  CITY 


ADVERTISEMENTS. 


xvii 


70  TON 
BUCYRUS    STEAM    SHOVEL 

Especially  Designed  for  Rock  Excavation, 


THE  BUCYRUS  COMPANY 


SOUTH  MILWAUKEE,  WIS. 


Manufacturers  of 

STEAM  SHOVELS 

DREDGERS  OF  EVERY  TYPE 

PLACER  DREDGING  MACHINERY 
RAILROAD  WRECKING  CRANES 

and  RAILROAD  PILE  DRIVERS 


Catalogues  on  application 


xviii  ADVERTISEMENTS. 


BOOKS 

HALBERT  R  GILLETTE 


"Rock  Excavation— Methods  and  Cost" 

Cloth,  5x7^  in.,  384  pages,  illustrated,        -        $3.00 

"Earthwork  and  Its  Cost" 

Cloth,  5x7^  in.,  256  pages,  illustrated,        -        $2.00 

"Economics  of  Road  Construction" 

Cloth,  6x9  in.,  40  pages,  illustrated,      -        -        $J.OO 


DESCRIPTIVE    CIRCULARS    ON    APPLICATION    TO 

Publisher  and  Bookseller 


M.  C  CLARK, 


13-21  Park  Row         -        -         NEW  YORK 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


Return  to  desk  from  which  borrowed. 


below. 


UN  1  2  1952 


LD  21-100m-ll,'49(B7146sl6)476 


YB  24060 


